Running counter to the real world idea of multi-taskers (Alton Brown, for one, says the only single-function device you should ever have is a fire extinguisher), I tend to love those little webapps that do one thing and do it well.
Dead simple: enter a song title and artist, and the Songerize app (powered by the streaming media service Seeqpod) serves it up for you.
Granted, it may not be the exact version you were looking for (I got a live version of Cheap Trick's "Dream Police," for example) and it's perhaps not as deeply populated as one would imagine (foiled it on the third try looking for "Tough It Out" by Webb Wilder.)
But if you're looking for that quick hit song lyric or something to bore out the earworm currently wedged in your head (and you don't want to launch iTunes or Rhapsody), this works well.
(h/t to Lifehacker)
UPDATE: Well, as of Sunday afternoon, something seems to be amiss with Songerize. Tried to again see how deep the catalog went, trying various random artists and songs the service may or may not have. Kept coming up with "Sorry, couldn't find song." Did this about a half dozen times, same result. Then I tried a song I knew it had ("Vertigo" from U2), same result. The only possible conclusion? I killed it. Me and my vast readership...