last.fm: personal music preferences

I first heard about last.fm about 2 months ago but had been slow to check it out.

It watches what music you listen to and makes suggestions from:

• music that is similar by genre, etc.
  
• other peoples' prefences whose are similar to your own
  

It has a radio player "thing" that also lets you rate songs and seems to be a free to air playlist.

Combining all this, it then lists what you listened to last, most, etc. Overall quite a lot of cool things going on behind the scenes with this. Check it out: