Thanks to Reivec for sending in this link to Tune Recycler. It's a project by those Downhill Battle rascals. Pepsi's giving away 100 million iTunes songs under Pepsi bottle caps and this is what Tune Recycler's all about:
With the Tune Recycler, you can send us your unwanted iTunes bottlecap codes and we'll use them to support independent music. Easy for you, and good for musicians.
Very cool. (PS: My 100% indie album is on iTunes.)