A couple of the most-frequently used books from our collection:
One of the best source books for bawdy and old-time cowboy songs we've run into is The Whorehouse Bells Were Ringing (and Other Songs Cowboys Sing), collected and edited by Guy Logsdon, another one from the University of Illinois Press, ISBN 0-252-06488-7 (paperback). Melody line shown for most of the songs.
Negro Folk Music U.S.A. by Harold Courlander, published by Dover in 1992, ISBN 0-486-27350-4.
A Treasury of American Ballads Gay, Naughty, and Classic, edited and with an intro and notes by Charles O'Brien Kennedy, published by the McBride Company, New York (1954), ISBN 54-12427. Many interesting songs (text), but no melodies.
Silverman's Guitarist's Treasury of Songs is a good addition to his two-volume Folk Song Encyclopedia mentioned above.
Excellent information in this thread--thanks, everyone!
Lin and John