Trying to find out who wrote, or who else performed, that song? Try BMI‘s Repertoire search, or ASCAP‘s ACE search. The Cover Songs Database appears to have its heart in the right place, but is very sparsely populated right now. On the other hand, The Covers Project has a mystifying desire to create "cover chains" ("A cover chain is a set of songs in which each song is a cover of a song by the band who covered the preceding song."), but the one spot check I did yielded better results than the Songs Databse, so it looks like a fine resource.