There are several, the best way I've found is to put a snippet of the lyric into something like google, and see what it comes up with. This is because the best site is usually a fan site, which isn't that easy to find without a search engine.
Also it's better to use the shortest exact phrase you know, rather than a longer and maybe wrong one.
I found Robert Plant's "Big Log" by this method, that song's lyrics had been going round in my head for years