Well, most people have heard about pandora radio at http://www.pandora.com, but this is different. Its called Musicovery. It lets you choose a genre and a ‘mood’, then it chooses songs that match your settings. It shows a map of songs and you can click on one to go to it. Very cool.
The main difference is that pandora has a lot of underground artists and a LOT more genres. You won’t be able to find the 80s hardcore band “Void” on this, or any style of music similar to it, but if you are into popular music you have already heard before than i guess this is a good site for you.