I imagine that most internet savvy people know about this already, but if not, Pandora Radio is great! You can enter your favorite musical artist and they will put together a custom (and free!) radio station with music from that artist plus others in the genre. I totally dig all their selections from other artists, which is introducing me to new music outside of my collection.



Pandora is also available for free on the iPhone!
http://www.pandora.com/