Looking for a thrift store near your home or when you're visiting a new city? TheThriftShopper.com is a great web site that will let you search by zip code to find stores in your area. As of May 2010 there are over 9300 stores listed nationwide (and they're always looking for more). They also provide forums to discuss various topics related to thrift store shopping and they allow you to rate your favorite thrift stores (scale of 1 to 5) so other visitors can get an idea of how great the deals are before they shop.
We absolutely love shopping at thrift stores — it's always an adventure and we always come away with great bargains on designer clothes.