Jake of the Web

Skreemr.com can find just about any song you are looking for: quickly, reliably, and for free. You can play the track before downloading it, or just play songs without downloading at all.

There are also additonal links that will automatically search for related lyrics, Wikipedia articles, YouTube videos, concert dates or pictures on Flickr:

At times when I am wanting to hear something in particular, I will do a Skreemr search (as opposed to Pandora, which is a great way to find new music).