This weekend on the Mall, a lot of the action will be outdoors with displays and exhibits -- including a ski tower, swimming pool and a model house -- focusing on the accomplishments of the handicapped.

It's all part of Inspire '85, an international forum and festival for disabled persons that also features singing, dancing, art shows and a whole spectrum of athletic events by and for the handicapped.

Admission to the following activities is free unless otherwise noted.

CHARLES COUNTY FAIR -- Friday, Saturday 9 to 10, Sunday 10 to 6, off U.S. 301, three miles south of LaPlata. Midway, 4-H horse show, baby show, farm and home exhibits, entertainment. Adults $2, children under 12 free. Free parking. 301/932-1234, 934-8377, 934-9240.

GREAT FREDERICK FAIR -- Friday and Saturday, 10 to 10, East Patrick Street, Frederick. Midway, livestock shows and sales, farm exhibits, arts and crafts, games. Adults $2, children under 10 free. 301/663-5895.

INSPIRE '85 -- Friday and Saturday, 10 to 5, The Mall (between 10th and 14th streets NW). International forum and festival for disabled persons features demonstrations, music, dancing, art shows and athletic events. 245-9186.

ARLINGTON HOSPITAL AUXILIARY AUCTION -- Friday, 6:30 p.m. (exhibition and silent auction), 7:30 p.m. (live auction), the Knights of Columbus Hall, 5115 Little Falls Rd., Arlington. Items donated by local retailers and individuals include two cars, Redskin tickets, symphony tickets and time at beach condos in Delaware and Maryland. All proceeds go to the Arlington Hospital. $5. 558-6595.

18TH-CENTURY MARKET FAIR -- Saturday and Sunday, 11 to 4:30, The Claude Moore Colonial Farm at Turkey Run, 6310 Old Georgetown Pike, McLean. The 18th century comes back to life with costumed tradesmen, craftsmen and artisans peddling their wares, period music and food, and games such as quoits, hopscotch and bobbing for apples. Adults $2; children under 12, $1. 703/442- 7557.

APPLE HARVEST FESTIVAL -- Saturday and Sunday, 10 to 6, Winchester Recreation Park, Winchester. 11th Annual Apple Harvest Arts & Crafts Festival includes the Virginia State Apple Butter Making Championship and a regional apple pie baking contest. Adults $2; senior citizens and children six through 13, $1; under six, free. 703/667-3826.

RECORD CONVENTION -- Saturday, 9 to 4:30, Holiday Inn (National Airport), 1489 Jefferson Davis Hwy., Crystal City. Where music lovers and collectors buy, sell and trade their discs. $2. 703/521-1600.

OLD TOWN TOUR -- Saturday and Monday, 10:30 a.m.; Sunday, 2, Ramsay House Visitors Center, 221 King St., Alexandria. Take a special tour retracing the steps of George Washington and Robert E. Lee with a colonial- attired guide through the cobblestoned streets of Old Town Alexandria. Adults $2; ages seven to 15, $1. 548-0100.

NEAT TO EAT -- Saturday, 10 a.m. to 11:30 a.m., Walney Visitor Center, Ellanor C. Lawrence Park, 5040 Walney Rd., Chantilly. Learn about different methods of preparing and preserving a harvest of wild edible plants.

VINES AND CLIMBERS -- Saturday, 10 to noon, Green Spring Farm Park Horitculture Center, 4603 Green Spring Rd., Annandale. A horticulturalist gives advice on how to spiff up your landscape with attractive vines and climbers. Phone reservations requested. $1. 642-5173.

LIBRARY BOOKSALE -- Saturday, 10 to 3, Glenarden Branch Library, 8724 Glenarden Pkwy., Glenarden. A "Rain or Shine Booksale" featuring hundreds of used and surplus library materials, most of which can be had for under $1. 699-3500.

RENAISSANCE FESTIVAL -- Saturday and Sunday, 10:30 to 6, Crownsville, Md. (take U.S. 50 east, then go north on Rte. 3, east on Rte. 450 to Crownsville Road, turn left for one mile which leads to the festival site). Jugglers, jousters and magicians along with other 16th-century characters come alive in this salute to the Renaissance. Adults 7.50; Seniors 6.50; 13 and under $3.50; five and under free. 261-1970.

SUITLAND EXTRAVAGANZA DAY -- Saturday, 11 a.m., William Beanes Community Center, 5108 Dianna Dr., Suitland. Squads of majorettes will demonstrate their baton-twirling skills; plus exhibits, a flea market and a softball game. 568-7719.

BACKYARD BIRD FEEDING -- Sunday, 1 p.m. and 3 p.m., Riverbend Nature Center, 8814 Jeffery Rd., Great Falls. Join a naturalist for a slide show, discussion and demonstration of feeder types, choice of bird feed, bird identification and solutions to special problems. 759-3211.

OUTDOOR COOKERY -- Sunday, 2 to 3, Hidden Pond Nature Center, 8511 Greeley Blvd., Springfield. Get an early start on next summer's outdoor cooking trends with this program exploring unconventional ways to cook food in the great outdoors. 451-9588.

FROM SEED TO CIGARETTE -- Sunday, 2 to 3:30, Walney Visitor Center, Ellanor C. Lawrence Park, 5040 Walney Rd., Chantilly. Visitors will learn about tobacco planting and harvesting techniques used in the 18th century; some planting for the adventurous. 631-0013.