Saturday's your chance to toe the line in your most battered pair of sneakers at the "Sixth Annual Scrungy Tennis Shoe Contest," sponsored by the Laurel Department of Parks and Recreation.

Using an intricate point system, based on the condition of the tongues, laces, soles and insides (but not odor), judges will determine the most gone-to-the-dogs pair of plimsolls. The winner receives new tennies and a trophy. Shoes may either be canvas or leather and must exhibit the results of natural wear and tear only; all ages may enter, but kids should be shoo-ins on this one.

All events are free unless otherwise noted.

NATIONAL ZOO -- Open daily; gates open from 8 to 8; animal buildings, 9 to 6; panda feedings, 11 and 3; elephant training demonstrations, 2; Sea lion training demonstrations, 2, 3001 Connecticut Ave. NW (Rock Creek Park), on the Metro Red Line. Family learning centers Zoolab and Birdlab open Friday through Sunday, noon to 3; Herplab open Wednesday through Sunday, noon to 3. 673-4717.

OXON HILL FARM -- Open daily, 8:30 to 5, Oxon Hill Road (take Beltway exit 3A, turn right on Oxon Hill Road). Saturday and Sunday, 1 to 3, "Horse and Wagon Rides." Free horse-drawn wagon rides; come early to see the team hitched. 839-1177.

NATIONAL AQUARIUM -- Open daily, 9 to 5, Department of Commerce, 14th and Constitution Avenue NW. The sharks are fed Monday, Wednesday and Saturday at 2; weekday features are a touch-tank, mini- theater and a thousand types of marine life. School groups should schedule in advance. Adults $1; children 50 cents. 377-2825.

CEDAR HILL -- Open daily, 9 to 4, 1411 W St. SE, Anacostia. Cedar Hill, Frederick Douglass' home, recalls his work with films, interpretive exhibits and a house tour. 426- 5961, 426-5962 or 426-5963.

USS BARRY -- Open daily, 10 to 5, Washington Navy Yard, Ninth and M streets SE. The Navy destroyer's weather deck is open for public viewing and self-guided tours. 433-3377.

CHILDREN'S MUSEUM -- Monday through Saturday, 10 to 4, Sunday 1 to 4, Rose Hill Children's Museum, north of Frederick. Take U.S. 15 north to Exit 8 to Motter Avenue; follow Motter to left onto 14th Street and left onto North Market Street, follow signs to Rose Hill. Costumed tour guides will conduct tours of the 1790 mansion. Hands-on exhibits include a loom, antique toys and spinning wheel. Adults $1; under 17, free. 301/694- 1646.

CAPITAL CHILDREN'S MUSEUM -- Daily, 10 to 5, 800 Third St. NE. Friday, 10:30; Saturday, 11, "Puppets on Parade." A variety show of colorful hand, rod and mouth puppets who perform musical numbers. Saturday, 2; Sunday, 3, "Spirit of Magic." Nestor the Magician saws people in half and makes animals disappear. Museum admission, $2; special performances an additional $2. 543- 8600.

DOLL'S HOUSE AND TOY MUSEUM -- Tuesday through Saturday, 10 to 5; Sunday, noon to 5, 5236 44th St. NW. A collection of antique dollhouses, dolls, toys, games and an exhibit of antique cat games and toys. Adults $2; under 14, $1; group rates available. 244- 0024.

CLOISTERS CHILDREN'S MUSEUM -- Wednesday through Friday, 10 to 4:30; Saturday, 12 to 4, 10440 Falls Rd., Brooklandville, Md., "Indian Summer Celebration." Hunt bear and porcupine hidden along a nature trail, dance around a totem pole and see an extensive Kachina doll exhibit. Saturday, museum hours, "Indian Crafts": make tepees, sandpaintings and decorate indian headbands. $2 donation requested from adults; group tours available. 301/823-2551.

RAILROAD STATION MUSEUM -- Wednesday through Saturday, 11 to 4; Sunday, noon to 5, Main Street and Maryland Avenue, Ellicott City. The renovated station has a diorama of the trip of Tom Thumb (an early 19th-century train) from Baltimore to Ellicott City. There are also sight and sound shows, model train exhibits and tours of the museum. Adults $1.25; under 13, 75 cents. 301/461-1944.

COLONIAL FARM -- Wednesday through Sunday, 10 to 4:30, Claude Moore Colonial Farm at Turkey Run, 6310 Old Georgetown Pike, McLean. Take a self-guided tour of farm life for a low-income family in Colonial Virginia. Demonstrations of agricultural and domestic chores, such as spinning and candlemaking, round out this history lesson. Adults $1; children under 12, 50 cents. 703/442-7557.

WOLF TRAP -- Friday, 10 to 1, Wolf Trap Performing Arts Center, 1551 Trap Road, Vienna. "Theater in the Woods." Contemporary dance, American folk music and children's theater. Programs free, but call for reservations and schedule. 255-1827.

ANACOSTIA NEIGHBORHOOD MUSEUM -- Friday 10 to 6; Saturday and Sunday, 1 to 6, 2405 Martin Luther King Jr. Ave. SE. Afro- American history lectures to ages four through eight as well as group tours and teaching services. 287-3369.

CHILDREN'S PLAYS -- Friday and Saturday, 8, Amphitheater, 2001 Bryan Point Rd., Accokeek, Md., "A Tale of Little Red Riding Hood: A Slightly Fractured Fairy Tale" and "The Good Giants and the Bad Pukwudgies." The Hard Bargain Kid's Theater presents these two one-act plays for children. Adults, $2; children and seniors, $1. 292-5665.

CHILDREN'S RADIO THEATER -- Saturday, 8 a.m., WPFW 89.3 FM. "The Emerald Prince," a story about a prince afraid of his own shadow and the help he enlists from a dwarf and dragon. Listeners can participate in a call-in following each program by calling 783-3104.

BATTING PRACTICE -- Saturday, 10 to 3; Sunday, 1:30 to 4:30; Tuesday and Thursday, 3 to 7:30, Tucker Road Community Park, 1771 Tucker Rd., Fort Washington, Md. Batting cage and automatic pitching machine; bats, balls and helmets provided. $1 for 20 balls; team reservations. 301/248-4404.

CARNIVAL DAYS -- Saturday and Sunday, 10 a.m. to 7 p.m., Pet Farm Park, 1228 Hunter Mill Rd., Vienna. Carnival Rides, games and live entertainment. $4, adults; $3.50 children ages two through 12. Admission includes free hayrides, tours and animal food. 759-3637.

TROLLEY MUSEUM -- Saturday and Sunday, noon to 5, Northwest Branch Regional Park, Bonifant Road between Layhill Road and New Hampshire Avenue, north of Wheaton. Trolley rides: $1, adults; under 18, 75 cents; under two, free. 384-9797.

STORYTELLING -- Saturday, 12:30 p.m., National Museum of African Art, 318 A St. NE, "Storytelling: Igbo Folktales." Experienced storytellers recount lore and history of the Igbo people of southeastern Nigeria. 357-2700.

CHILDREN'S PLANETARIUM -- Saturday and Sunday, 1 and 4, Rock Creek Nature Center, 5200 Glover Rd. NW. First show for children four to seven (must be accompanied by an adult); second show for ages seven and up. No latecomers are admitted. 426-6829.

ADVENTURE THEATER -- Saturday and Sunday, 1:30 and 3:30, Adventure Theater, Glen Echo Park, Glen Echo. "Toby Tyler," the story of a young boy who runs off to check out life under the big top. $3, group rates available. 320-5331 weekdays and performance days from 10 to 2.

SCRUNGY SHOE CONTEST -- Saturday, 2, Laurel Municipal Swimming Pool, Ninth and Main streets, Laurel (Take I-95 north toward Baltimore; exit on Rte. 198 east into Laurel, turn left after second light. Pool is at the end of the street.), "Sixth Annual Scrungy Tennis Shoe Contest." Break out those battered sneakers and show them off; condition of shoes must be a result of natural wear. Register between 1 and 2, day of the event. 776-7419.

PRINCE WILLIAM FOREST PARK -- Nature Center, near Quantico, (take I-95 to Rte. 619 west; park entrance 1/2 mile on right; follow signs to nature center). Saturday, 2, "Snake Feeding Demonstration," see a king snake, black rat snake and mole snake feed on live prey; 3 to 4, "Children's Hour," kids six to 12 can join a ranger for a nature walk to learn about forest conservation, how to read trails and more. Sunday, 1, "Orienteering for Kids," join a ranger to learn basic compass skills to get you through the woods. 703/221-2104.

DRAW-IN -- Sunday, 12:30 to 5, The Naturalist Center, Museum of Natural History, 10th and Constitution Avenue NW, "Draw-In." Kids 12 and up can drop in with their sketch pads and pens, pencils and crayons to draw fossils, bones, rocks and other objects in the museum. Artists will be on hand to offer assistance; children must be accompanied by an adult. Ask for directions at the museum information desk at entrance. 357-1503.