MICRONESIA is a magnet for volunteers.The United States Peace Corps, the Japanese Overseas Volunteers (JOV), Pacific Missionary Aviation (PMA), and various other volunteer groups have set up operations on the islands. The Peace Corps has been operating on the islands since 1966. At its high point there were more than 700 volunteers here. Today there are 75 volunteers in Micronesia and on Belau, an island west of Micronesia still under United Nations trusteeship. The Peace Corps has tried different strategies, including teaching English as a second language. Today, Jeff Robertson, director of operations in Micronesia, says the Peace Corps gives emphasis to specific projects for which Micronesia or state governments request help. "We see ourselves as a human-resource development agency," says Mr. Robertson. One two-year-old Peace Corps project is a youth leadership camp. Sixty children from all the islands are invited each summer to learn arts and crafts as well as listen to talks on suicide prevention, substance abuse, and AIDS. Holly Gunby, a volunteer from Seattle, recently helped organize a small "ecotourism" project at the base of Sokehs Rock on Pohnpei. The project involved installing stairs on the trail up the hill. In the past, hikers have unwittingly trampled yams and other edible roots grown on private property. Ms. Gunby helped to find $8,000 in funding for the trail, which was built with volunteer labor supplied by a youth group. Japanese aid has focused on developing fishing and agriculture projects, including culturing giant clams and vegetable farming. "The islands generally import most of their vegetables," says Akio Yamamoto, director of JOV. The Japanese project will show native farmers how to grow cucumbers, Chinese cabbage, and okra. Pacific Missionary Aviation has seven active aircraft providing free medical evacuations, dropping medical supplies, searching for missing fishermen, and returning human remains for burial. Begun in 1974 by the Rev. Edmund Kalau, the service survives mainly on contributions from members of the Lutheran faith in the US, Germany, and Switzerland. PMA flies to isolated atolls that do not have any air service.