From time to time, I'll go to a store that sells music and browse their used section, then pick out an album (or a few) that I've never heard of but that looks interesting. There are hits and misses, of course. The misses don't hurt much when the CDs can cost as little as a dollar, and when I get a hit in this way there's just something really cool about it. Some of my tactics for increasing my success rate:
-Look for interesting album artwork.
-CDs packaged in digipaks instead of jewel cases seem more likely to fit my tastes (not that I ignore those in jewel cases).