I cant tell you how much I love Songza. It's great b/c I can listen to songs, for free, and I dont need to download anything.
When you get the search results for your song, and click on one you want to listen to, a symbol similar to the red baron's cross pops up. From there you can play the song, rate it, share it with friends, or one of their newer features, add that song to a play list!
Granted, you cant take it with you when you go out (unless you have one of those blackberry/iPhone things, but then if you have one of those, you would more likely have songs ON your phone and not streaming them from some internet site).
But it's really good when you're working on the computer, doing stuff, and dont feel like popping in a CD.