WORKS BY FRENCH ARTIST JEAN ARP (1886-1966) ARE being presented in a major retrospective that opened last week at Boston's Museum of Fine Arts (through Sept. 13). Gallery talks on Arp's work will be given July 12 and 16 and Aug. 15 and 27. The exhibition, which has already been seen in Europe and Minneapolis, will conclude its US tour at the San Francisco Museum of Modern Art, Dec. 3-Jan. 31, 1988. NEW DRAMATISTS HAS CHOSEN FIVE NEW PLAYWRIGHTS for 5-year memberships, out of nearly 300 applicants. They are Migdalia Cruz, Lisa Loomer, Milcha Sanchez-Scott, Susan Yankowitz and Y York. The program assists playwrights in developing their scripts in workshops and readings and in dealing with day-to-day career problems. Past and present members comprise a cross section of leading contemporary American dramatists. WATERVILLE VALLEY FESTIVAL OF THE ARTS BEGINS its third season of rock, jazz, folk, and classical concerts this Friday in the White Mountain National Forest (N.H.). Acts include Spyro Gyra, folk singer Tom Rush, fiddler David Holt, guitarist Chet Atkins, the Preservation Hall Jazz Band, Dizzy Gillespie, the Paul Winter Consort, chamber music, and children's programs. Also offered are workshops in ``Folk Rap,'' clogging, dulcimer, and blues harmonica. Festival ends Aug. 9. For details, call 1-800-258-8988, or 1-800-5523-4767 in New Hampshire.