THE COUNTY and state fair season is off and running -- in just about every conceivable way -- beginning this Friday with the Prince William County Fair in Manassas.

For starters, ostrich racing makes its area debut there with celebrities riding behind 400- pound birds built for speeds of up to 40 miles per hour. Drivers use brooms to steer and a full-nelson to wrestle the ostriches to a halt. Sounds more fun to watch, doesn't it?

In the coming weeks:

* Over in Montgomery County, there'll be pig racing five times daily, along with hog-calling contests. And don't miss the expanded demolition derby, the cowchip-throwing contest and appearances by the U.S. Marine Drum and Bugle Corps and silent drill team.

And, finally, proving it's not only pigs who love mud, the fair will feature a "Monsters on Wheels Mud Bogg," with four-wheelers jacked up so high they'll drive over other cars and through the mud.

* The Fredericksburg Agricultural Fair will also get down to earth with four-wheelers sloshing around in 8,000 gallons of water and mud. But you won't find that sort of thing in Arlington, where the annual get-together is billed as the only "completely urban county fair" in the area.

* For more traditional racing, try the Maryland State Fair in Timonium where there'll be thoroughbred racing; for harness racing, try the Shenandoah County Fair in Woodstock and the West Virginia State Fair in Fairlea.

Standard fare this season at most county and state fairs includes tractor pulls, 4-H and FFA exhibits, midways, country music, arts and crafts, livestock auctions and more. Here's a wrap-up of fairs within three hours of Washington. (Entrance fee to fairgrounds does not necessarily include admission to big name concerts, rides and special events. It's recommended to check with the fairgrounds beforehand.) FAIR AFFAIRS MARYLAND

SUNDAY THROUGH AUGUST 17: Howard County Fair, West Friendship. Out Georgia Avenue to Route 144, turn right to the fairgrounds. Hours: Sunday noon to 10:30; Monday to Saturday 9 a.m. to 10:30. Admission: $2, 12 and older; free, 11 and under. On weekdays, $1 for 62 and older. Free parking. Phone 301/442-1022.

Agricultural and industrial exhibits; baked goods; 4-H exhibits; arts and crafts; photography; talent show; horse, cattle and livestock shows; livestock sales and horse pulls; baby contest; nightly entertainment.

Opening day contests: pie-eating, cow-milking, tobacco- spitting and Howard County farm queen. AUGUST 19-24: Montgomery County Fair, Gaithersburg, off I-270. Hours 7 a.m. to midnight. Sneak preview August 18, adult admission $1; children under 12 free. All other days adults $3; children 12 to 15, $2; under 12 free. Parking $2 on the grounds. Tuesday is children's day; 18 and under are free until 6 p.m. Exhibit halls and commercial exhibits open at 9 a.m. Phone 926-3100 or 948-5794.

Special Events: Arabian horse show at 8 a.m. on August 18 followed by the Kingdom Seekers gospel music at 5 p.m. Additional musical entertainment at 7 and 9 p.m. by the Trinidad Tripoli Steel Band.

Pig racing five times daily. Country music performances, household demonstrations (candy making, microwave cooking, breadmaking, meatcutting and seafood), craft exhibits, non-stop bingo, livestock shows and sales, tractor pulls, draft horses.

Maryland Porkecue cook-off, and tractor pull, Wednesday; U.S. Marine Drum and Bugle Corps and silent drill team, 5 p.m. Wednesday; demolition derby Thursday and Friday; antique tractor pull and the Monsters on Wheels Mud Bogg, Saturday; Port Authority (Navy band), Saturday; Canadian country music star Ronnie Prophet, Saturday, 8 and 10 p.m.

AUGUST 24-SEPTEMBER 2: Maryland State Fair, at the State Fairgrounds, Timonium. Off I-83 north, exit 17. Hours; 10 to 10 for exhibit halls, noon to 11 for midway. Admission $2.50, includes thoroughbred racing. Monday- Friday special, noon to 4, all rides for a total of $3 plus admission. Parking $1. Phone 301/252-0200.

Midway, livestock shows and sales, agricultural and industrial exhibits, arts and crafts competitions, cattle and pony shows.

Nine daily horse races, ten on Saturdays and Labor Day. Racing on both Sundays. Post time, 1. The Hub Caps, classic doo-wop, 8 and 10:30 August 24, 9 p.m. on August 25. On Labor Day, Frankie Vali and the Four Seasons at 7 p.m. in grandstand. Call 301/252-0200 for ticket information.

SEPTEMBER 11-15 -- Anne Arundel County Fair, Crownsville. From U.S. 50 east, exit at Parole/Crownsville. Go west on Route 178 four miles to Crownsville, follow signs to new fairgrounds. Hours Wednesday and Friday 4 p.m. to 11 p.m.; Thursday 1 to 11. Saturday 9 to 11; Sunday, 9 to 8. Admission $2, ages 11 and older; $1 ages six to 10; $1.50, 62 and older -- I.D. required. Phone 301/923-3400 and 301/761-3473.

Midway; horse shows; horseshoe pitching; small livestock, handicraft, farm, garden, home, flower and 4-H exhibits. Dance demonstrations, fair queen and baby contests, senior citizens talent show, hog calling, watermelon eating, tractor driving, tug-o-wars (between fire and police departments), pet parade, draft horse pulls, jazz, bluegrass and rock groups.

SEPTEMBER 12-15: Prince George's County Fair, county equestrian center, Upper Marlboro. At U.S. 301 and Route 4. Hours 11 to 10 daily. Admission $4; ages seven to 12, $2; under six are free; 55 and older, $2. Parking $1. Phone 301/441-1303 or 952-0270, after August 16.

Free hot-air balloon rides, scarecrow-making workshops, 4-H and open class agricultural and livestock exhibits, horse shows, midway, musical entertainment. Competitions for cloggers, firefighter brigades, cow-chip throwers, tobacco spitters and country-western battle of the bands. Friday, 8, '50s rock 'n' roll by The Hub Caps; pig racing, Saturday and Sunday.

SEPTEMBER 16-21: Great Frederick Fair, East Patrick Street, Frederick. Take the first Frederick exit on I-270 and follow signs to fairgrounds. Hours: 10 to 10. All musical performances at 6:30 and 9. Admission $2; children under 10, free. Phone 301/663-5895.

Midway, livestock shows and sales, agricultural and farm equipment exhibits, arts and crafts shows, tractor pulls (Monday and Tuesday, 6:30 p.m.) and games.

Entertainment includes the Statler Brothers on Wednesday; demolition derby on Thursday; Mickey Gilley and Reba McEntire on Friday; Hell Drivers at 1, Charley Pride and Lynn Anderson on Saturday.

SEPTEMBER 19-22: Charles County Fair. Off U.S. 301, three miles south of LaPlata. Hours: Thursday 5 to 10; Friday-Saturday 9 to 10; Sunday 10 to 6. Admission $2; children under 12, free. (Friday,all students are admitted free until 5 p.m.) Free parking; complete handicapped access. Phone 301/932-1234, 934-8377, 934-9240. Midway, selection of Queen Nicotina, draft horse pull, 4-H horse show, talent show, teen dance, baby show, junior livestock shows and farm and home exhibits and musical entertainment.

SEPTEMBER 26-29: St. Mary's County Fair, St. Mary's County Fairgrounds. On Maryland Route 5, two miles south of Leonardtown. Hours: Thursday 4 to 9; Friday- Saturday, 9 to 10; Sunday 9 to 6. Admission: $2 adults; children six to 16, $1; children under six, free. (Four-day pass available for $4 per person). Phone 301/475-2707, 475-9388 or 475-5694 during fair days.

Agricultural exhibits, photography, arts and crafts, baby show, horse shows, jousting competitions, draft horse pulls. Livestock sale on Saturday. Entertainment by gospel singers, square dancers, country-bluegrass and American popular song groups.

OCTOBER 3-6: Calvert County Fair, Fairgrounds, Prince Frederick. Take Route 4 to Prince Frederick; turn left on Dares Beach Road. Go 1/4 mile. Hours: Thursday 4 to 11; Friday-Saturday 10 to 11; Sunday 10 to 8. Admission $2 Thursday-Saturday; $5 Sunday; 12 and under free. Phone 301/535-0580 or 301/535-0026.

Parade, talent show, battle of the bands, dancing, lightweight and heavyweight horse-pull contests, Little Miss contest, baby contest, dance exhibitions, tractor and 4-wheel pulls, various musical entertainment. VIRGINIA

FRIDAY & SATURDAY: Warren County Agricultural & Industrial Fair, six miles north of Front Royal. From I-66 to U.S. 522 north, to fairgrounds about four miles up on the right. Hours: Gates open Friday at 6; Saturday at 4. Closing time roughly 11 to midnight. Admission $3; ages 12 and under free. Phone 703/635-3013.

Country and American popular performances on Friday and Saturday nights, carnival, helicopter rides, agricultural, industrial, housewares and livestock exhibits.

FRIDAY THROUGH AUGUST 17: Prince William County Fair. From I-66, take Route 234 south of Manassas. Hours: gates open at noon each day and close roughly at midnight. "Pay Once -- Do It All" admission is $6 each day; 60 years and older, $3; under three years free. Free parking. Admission price includes all grandstand events, exhibits, rides on the midway and animal circus; ticket price does not include admission to shows that require proof of age, 18-or-older. Phone 703/368-0173.

Tractor pulls, games, beauty and swimsuit contests, livestock and agricultural exhibits and rock concerts. This Friday "Country Music Spectacular" with Billy "Crash" Craddock and Michael Twitty at 7 and 9. Truck and tractor pulls Saturday night and next Friday evening. Ostrich racing and animal acts on Monday; demolition derby at 7:30 followed by rock from the Atom Smasher Band Tuesday; Country music from Sawyer Brown and the Country Gentlemen at 7 and 9. Thursday evening at 7 and 9, rock with Muglestons.

AUGUST 18-24: Page Valley Agricultural & Industrial Fair, Luray. Take I-66 to the Front Royal exit. South on U.S. 340. Left on U.S. business (East Main) and follow signs. Admission $2; age six to 12, $1. Hours: Opens Sunday at 1; Saturday at 2:30; weekday openings vary. Open until midnight every night. Phone 703/743-5665.

Horse show, baby contest, beauty pageant on opening day. 4-H, FFA heifer and steer shows; hog, lamb and dairy shows; 4-H Olympic Day, pet show and fashion shows. Demolition derby, Friday at 7. ATC Trymoto drag races, Saturday at 2:30 followed by local entertainment. Musical entertainment includes the Younger Brothers Band on Monday and Michael Twitty on Wednesday; both performances at 8 and 10.

AUGUST 19-24: Clarke County Fair, Berryville. Take I-66 west to U.S. 50 to Route 340 north to Berryville. Go a mile west on Route 7 to fairgrounds. Hours: Monday, at 9 a.m., every other day at 8 a.m. Closing time is roughly midnight, sometimes later; Pre-schoolers admitted free; children 15 and under, $1; adults $2. Season tickets good all week: adults $8; children $3. Phone 703/955-3106.

Livestock, home arts, horticultural exhibits, carnival, horse pull and beauty contests. Horse shows Thursday at 9 a.m., Friday at 8:30 a.m., Saturday at 9 a.m. Fireworks on Friday and Saturday around midnight. Entertainment includes country and bluegrass, calf and greased-pig scrambles and tractor pulls. Beef and chicken barbecue begins at 5, Wednesday-Saturday.

AUGUST 19-24: Greater Shenandoah County Fair, Waynesboro. Take U.S 29 south to Charlottesville. Then I-64 west to Waynesboro to U.S. 340 north to Eastside Speedway. Hours: 5 p.m. until 11; open until midnight on Saturday. Admission $2.50 per car, includes parking. Phone 703/943-6925.

Fifty-lap oval track racing Tuesday and Saturday; demolition derby, Wednesday; country music from the Judds, Thursday, 7 and 9; rock 'n' roll night, Friday. Beauty contest and professional mud wrestling, Monday. Midway includes about 20 rides and shows. Petting zoo, agricultural and homemaking exhibits, greased-pole climbing, but no livestock.

AUGUST 22-25: Arlington County Fair, Thomas Jefferson Community Center, 3501 Second St. South, at the intersection of Arlington Boulevard and Glebe Road. Hours Thursday, 7 p.m. to 10, Friday-Saturday, 10 to 9; Sunday, noon to 6. 558-2475.

This is a mostly indoor, suburban-style community fair with vegetable exhibitions and photography, crafts and baked goods competitions; local civic organizations, homecrafters and handicrafters and politicians will also have booths. Barbershop quartet and other live entertainment.

AUGUST 25-31: Shenandoah County Fair, Woodstock. Take I-66 west to I-81. South on I-81 to exit 72. Hours: noon to midnight. Admission: $2.50 adults; children 8 to 12, $1.50; free for school children on August 25-26. Harness racing Wednesday-Saturday; post time is 2 p.m. Grandstand admission: $1, adults; 50 cents, children. Virginia does not offer legalized parimutuel wagering. $1 parking. Phone 703/459-3867.

Midway, livestock, horse show, agricultural and industrial exhibits. Beauty pageant, tractor pull, demolition derby, livestock auction, barbecue chicken, pork and beef. Musical entertainment by the Judds, Tuesday; Lou DeWitt, Thursday; Mel Daniel, Friday; Susquehanna River Band, Saturday.

AUGUST 30-SEPTEMBER 7: Fredericksburg Agricultural Fair. Take I-95 south to first Fredericksburg exit. Turn left on U.S. 17; pass through business district to fairgrounds. Hours: weekdays open at 5 p.m.; Saturday, Sunday and Labor Day open at noon until 11 p.m. or midnight each evening. Admission $3 weekdays and first weekend; $5 per day on Labor Day weekend; includes parking and all rides. Phone 703/371-1143.

Agricultural, livestock and arts and crafts exhibits and regional talent and baby contests. Mud buggy truck pull, Saturday at 3 p.m.; discotheque nightly, $1 admission fee; tractor pulls on both Friday nights during the fair; a beauty pageant on Labor Day. Country and bluegrass entertainment nightly.

SEPTEMBER 19-29: State Fair of Virginia, Richmond. Take I-95 south to Richmond and follow signs as you reach the northeast city limits; exit 17. Hours: 8 a.m. to midnight, exhibit buildings open 10 to 10. Admission: $7.95; advance sales $5.95; covers all carnival rides, grandstand shows, circus events and parking. Phone 804/329-4437

This year's theme is "85's Galaxy of Fun," all kinds of entertainment, soul music concert, country music, contests; six pig races a day. Each year attracts more than half a million visitors. Offers Hanneford Family Circus, the Ron Urban Ice Show and nonstop livestock events and exhibitions. An enlarged American Heritage Showcase (20 tents) recreating the lifestyle of turn-of- the-century America with household implements, winemaking equipment, old-fashioned store, antiques, old cars, tractors and bicycles. Genuine medicine show performed by Dan Barth's Old-Time Medicine Show and singer Marita Brake.

For additional Virginia fair information, call W.R. Cobb at the Virginia Association for Fairs at 804/786-3951. WEST VIRGINA

AUGUST 16-24: West Virginia State Fair, Fairlea. Take I-66 west to I-81. Go south to I-64, then west on I-64 to the Lewisburg exit. Take Route 219 south two miles to Fairlea. Hours 8 a.m. to midnight. Admission $3.50 adults; under 13 free. August 16, $7 admission includes all rides and shows. Concert prices other days range from $4 to $12.

Harness racing, horse shows, champion livestock auction, draft horse pulling contest, 4-H demonstrations, midway, West Virginia crafts. Free circus.

Performances by Billy "Crash" Craddock, August 16; Survivor, August 17; Tom Jones, August 18; The Buckinghams, The Turtles, Gary Lewis and the Playboys and the Grassroots, August 19; Jerry Reed, August 20; Tammy Wynette, August 21; Mack Davis, August 22; Charley Pride, August 23; the Statler Brothers, August 24.