Frank, is that Cecil Sharp book still in print? His fame as a song collector is right up there with Child, isn't it?
Another good one is "Songs of the Sailor and Lumberman," by William Main Doerflinger. This was originally published in 1951 as "Shantymen and Shantyboys." My 1990 edition was published by Meyerbooks, Box 427, Glenwood, Illinois 60425 - priced at $19.95. I don't know if it's still in print. I found it used at a bargain price (gloat!).
Sing Out! publishes a number of songbooks other than RUS - their two "Reprints" collections are very generous collections of songs that were printed in the magazine from 1959-73. There's a labor songbook by Pete Seeger and Bob Reiser called "Carry It On"; and Pete's "Where Have All The Flowers Gone" is a very entertaining collection.
Another interesting book is "the Incompleat Folksinger," by Pete Seeger, edited by Jo Metcalf Schwartz. It was reprinted by the University of Nebraska Press in 1992. this one is not just a songbook - it's a journey through Pete's world of folk music, with songs, tips on playing various instruments, and stories about Pete and the musicians he had as friends. Good book.
-Joe Offer-