A giant online swap meet for used CDs might not sound too exciting on the surface, but Lala.com is one of the most engaging Internet music services we've ever come across.
The concept is elegantly simple: You create an account, log on, then list the CDs you have and those that you want. The service automatically sends you an e-mail whenever a CD on your "Have List" is matched up with a disc on another member's "Want List." By trading CDs on your Have List to other members, you earn "karma."
The more karma you have, the more CDs you receive from other members. You don't have to scour other members' profiles to find matches; Lala handles that automatically. Best of all, you pay only $1.75 including shipping for each CD you receive. And there's no charge for sending discs to other members.