One contagion in publishing these days that no one is complaining about is the proliferation of books that ferret out free and low-cost things that can be ordered by mail. Two of local interest are Something for Nothing by Washington Researcher's chairman Matthew Lesko and The Freebies Book, compiled by Elaine Jorpeland and Ilsa Whittemore for the American Society of Association Executives. Lesko's book jolts readers into realizing that their tax dollars are supporting numerous government research projects, publications and services that are cheap, or free, for the asking. He groups them into three categories. First, the sources of facts, which include hotlines, publications and research services. Second, the freebies, among them a free plastic water-saving device for inserting in the shower head. Finally, the government gold mines known as loans and grants. ($2.95 from Something for Nothing, AP Newsfeatures, Box G22, Teaneck, N.J. 07666). The Freebies Book round up an abundance of pamphlets and promotional items put out by associations, covering health, home buying and building, maintaining and buying a car, getting by in business, choosing a career and finding leisurely pursuits ($4.95 from American Society of Association Executives, 1575 I St. NW, Washington, D.C. 20005).