blanks & postage
I'm just getting into the whole b&p community, but so far I've found some of the best live music I've ever heard. B&P stands for blanks and postage. Basically, you send someone blank CDs and postage/envelopes to mail the CDs back to you, and they'll burn the music for you free of charge. The key to starting this is to find a b&p community with the artist/music you like, and hang around the message boards. I've found a really good one for The Dave Matthews Band. Through this message board I've already acquired over 70 shows. I even found the show that my brother and I went to on 04.30.2002. So I got a copy of it and burned one for each of us.
You can post your list online if you want to do a b&p or trade music other people. This is a great way to increase your music collection. You can find my list here.
For a more detailed description of the b&p process, go here.