I'm guessing a lot of you will already know about this, but I haven't found it mentioned on these forums so here's the best thing on the internet....ever... (Disclaimer:imho)

www.pandora.com

Create your own radio stations by adding the names of bands/songs you like and start getting their tracks played to you.
But the clever bit is that it's part of a project to attempt to "classify" music, which means that it also plays you stuff you didn't ask for, but which it "thinks" you may like.
You then give the song a or a and it adjusts the music played on that station to suit your taste.

Scarily it's quite good - I've found loads of great music I never would have come across if I was just using the iPod.

...oh, and it's completely free.



P.S.
Setup different stations for the different styles of music you like(heavy/pop/whatever). It does get confused if you say to Clutch then to Portishead - the last time that happened the damn thing went on to spend an entire friday afternoon utterly convinced I would like to savor the varied and magnificent output of "Gloria Estefan and the Miami Sound Machine".

I like it.

It's a brilliant idea.
I've only just started playing with it, I'll let you know how it does with Belle and Sebastian mixed with Death Cab For Cutie, Beastie Boys and Nine Inch Nails...pretty eclectic!

And a zipcode to help you join 10109

Good find