IN CONJUNCTION with the 4th Annual ADD Arts Festival (see Weekend's Best on page 3), free films will be shown at the Martin Luther King Jr. Memorial Library (Ninth and G NW, Room A-5) Sunday from noon to 10:30. The first two films, The Red Balloon and Miracle in Harlem (at 2) are for younger audiences. The program continues at 3:30 with Les Blank's Gap-Toothed Women; Amran Nowack's Isaac in America, a portrait of Isaac Bashevis Singer, at 4; Storme: Lady of the Jewel Box Revue, local filmmaker Michelle Parkerson's documentary on female impersonator Storme De Larverie, at 5; Sitting in Limbo, a Canadian film about black adolescents struggling with unemployment and pregnancy, by John N. Smith, at 5:30; Gene Feldman's Marilyn Monroe -- Beyond the Legend, at 7; and Ross McElwee's popular documentary, Sherman's March, at 8 . . .

The American Film Institute's September-October program will have two festivals -- Yugoslav and Latin American; a tribute to the Ismail Merchant/James Ivory/Ruth Prawer Jhabvala team (that brought us Room With a View among other things); as well as films on Sherlock Holmes, the Vietnam experience, and more. This weekend (Friday and Sunday), under the ongoing theme "Preview/Review," the AFI will premiere Captive, a film by Paul Mayersberg (who penned The Man Who Fell to Earth for Nicolas Roeg), about a Patty Hearst-style kidnapping, and featuring Oliver Reed. It's double-billed with Ken Russell's adaptation of Women in Love, also with Reed, Glenda Jackson and Alan Bates. The program is at 8:45 Friday and 8:15 Sunday. Tickets are $4.50, $3.50 for members.

John Ford's tried-and-true The Searchers will be screened free at the National Gallery of Art's East Building Saturday at 2:30. John Wayne plays Ethan Edwards, a cowboy tracking down his daughter and her kidnappers. Also free at the East Building Sunday at 4, communications professor Robert Kolker will show West German director Wim Wenders' 1982 The State of Things, after a lecture called "The Composition of Narrative: How Movie Images Tell Stories."

The Smithsonian Resident Associates offer four recent Czech films starting this Tuesday with Jaroslav Soukup's Fists in the Darkness (1986); Juraj Jakubisko's A Thousand Year Old Bee (1983) on September 15; Karel Kachyna's Forbidden Dreams (1986), September 22; and Vit Olmer's Anthony's Chance (1986), September 29. Showtimes, at the National Museum of American History's Carmichael Auditorium, are at 7. Admission is $24 for non-members. 357-3030 . . .

Thursday at 1, free: Soto, a New Vision of the Art, a Spanish-language film about Venezuelan kinetic artist J.R. Soto, at the Organization of American States' General Secretariat Building (1889 F St. NW, 6th floor, Room B). 458-3673.