WikiFM - not the most beautiful site to look at, but I already love it.

The premise for this Mashup is very simple: divide the page into two frames,

• load a Last.FM player in one and
• show the related Wikipedia page in the other,

...according to whatever is playing at the moment.

You can search by artists, tag, user name, group; alternatively you can simply enter a Last.FM URL. Last.FM is by itself a fantastic place to read about music while you’re listening to it, due to their detailed info pages for each artist. Go to http://james.nerdiphythesoul.com/wikifm/ to listen and find out for yourself.