Ruddigore--Gilbert & Sullivan and a witch's curse. At AGASSIZ.

Salome--Oscar Wilde at the CRAFT EXPERIMENTAL THEATRE, 96 Brookline Ave., Boston (262-7777).

Schweyk in the Second World War--Brecht's play in a radical adaptation by Charles Sabel. At ELIOT HOUSE.

The Slave & Birdbath--Two one-acters by LeRoi Jones and Leonard Melfi, respectively. Everyone knows about Mr. Jones, but few know about Mr. Melfi, a fine Cafe Le Mama playwright with a poet's heart. At the ATMA, 498 Tremont (338-9791).

You're a Good Man, Charlie Brown--Which somehow works. At the WILBUR (426-9366).

SCREEN

At the Circus--Not among the Marx Brothers best, but still funnier than anything else around, save their "Night at the Opera." Before this movie is over, Margaret Dumont is shot out of a cannon, and Groucho gets to sing an Arlen-Harburg number about a tattooed lady. At the SYMPHONY II, Huntington at Mass. Ave. (262-8837).

Barbarella--Roger, Vadim's very public salute to Jane Fonda; more or less what you'd expect. At the CIRCLE, Cleveland Circle, Brookline (566-4040).

The Boston Strangler--Believe, your worst suspicions. At the MUSIC HALL, Tremont St. near Stuart (423-3300).

Camelot--An overblown adaptation of the Lerner & Lowe musical, with Richard Harris and Vanessa Redgrave. But swell music. At the FRESH POND in Fresh Pond, Cambridge (547-8800).

Les Carabiniers--Godard. Sunday at the HARVARD-EPWORTH CHURCH, 1555 Mass. Ave.

Closely Watched Trains--Funny and sad like most Czech films. Worth seeing. At the HARVARD SQUARE (864-4580).

Coogan's Bluff--One of Donald Siegel's ("Invasion of the Body Snatchers," "Madigan") finest films, its pleasantly mechanical script completely transcended by the honesty and directness of Siegel's style and a moral concern for the fate of his characters. Clint East-wood is fabulous, and the Siegel stock company (Susan Clark, Don Stroud) again proves a group of Hollywood's most capable new actors. Marred only by an unfortunately pedestrian last 60 seconds. At the ORPHEUM, Washington St. (542-5557).

Dear John--A Swedish film about a romance between two not-so-young and not-so-beautiful people. Well acted, but boring in spots. At the HARVARD SQUARE (864-4580).

Finian's Rainbow--A heavyhanded, poorly acted film version of the musical, with nothing but the splendid score and the magnificent Fred Astaire to recommend it. The director, Francis Fred Coppola, has a bad habit of chopping people's hands and feet off; stars Petula Clark and Tommy Steele ought to act their age. At the SAXON, Tremont and Stuart (542-4600).