www.pandora.com
My brother is visiting me in North Carolina this weekend. This morning I was about to launch my internet Sirius and play some music while we made breakfast for the families. My brother told me about this site. You type in a name of a band or song and it finds that artist then finds similar songs / artists and plays them as well.
Right now I am listening to my Elton John channel it made for me, it first played Daniel by Elton then Summer Highland Falls by Billy Joel and now its playing cool change by Little River Band.
Check it out, its really cool.