When I lived in DC, I would visit the thrift shops in the military bases.
Military personnel donate to thrift shops, I am hypothesizing, due to the limited space/cargo that can be transported from one duty station to the next - not because it is a piece of junk. I found some really cool stuff like a replica of Napoleon's dagger for $10 or barely used roller blades for $7.
Depending on what part of town, Goodwill and Salvation Army have some great stuff. I recall hearing on NPR that more and more people go there due to the economic issues in this country. The best thrift shops, I have heard, are in South Florida where there are high end designer clothing and accessories for women. I have never been there, but I would think that there are equivalent high end things for men, too.
Thrift Stores Go Upscale : NPR