Oberlin College Libraries and Sing Out! brings us this invaluable resource. "An index to traditional folk songs of the world with an emphasis on English-language songs. Each entry includes the song title, first line of chorus, first line of verse, and full bibliographic information on the source. The index contains over 42,700 entries, and, to date, indexes over 2,225 anthologies."
Once you find the anthology that has the song you want, search our online library catalog for the song to see if we have it.