What online site has the biggest authorized selection of music? Is it iTunes? Nope. Amazon's MP3 store? Wrong again. It's actually Last.fm, an online radio station that's managed to snag music from all four major labels as well as music from a whopping 150,000 independants.

The catch? You can't buy any of it to own. But it's all free to stream, and all of the artists get reimbursed for their work through advertising. And the site also tracks what you listen to (both using their service and through iTunes), allowing it to recommend new music you'd like and creating custom radio stations just for you. It's a pretty awesome service, and even if it's not going to replace your permanent collection, it's a great way to listen and try new stuff at your computer.

Via Last.fm