I signed up at Last.fm in 2005. I never really used it a lot. Until recently, when I got slightly bored by soma.fm (still great though!). I found out Last.fm is streaming tons of music. A bit like pandora.com, but way better. And it seems they have everything, ranging from Aphex Twin, to the Beatles, your local punk band, Ravi Shankar, Stockhausen, anything.
It can give you recommendations, or you listen to a tag radio (try gypsy, 303, amsterdam, whatever). You can click "love" if you like something and "ban" is even more useful. It's especially nice to tune into your friends' radios. Feel free to tune into mine.
There's even a client for my Nokia N810. Now we just need free wireless everywhere...