I have always like Savers (in the Northwest it's called Value Village). Of course, as thrift stores go, it's sometimes hit-and-miss. But what I like about this thrift store in particular is that it's big (which equals big selection), it's not overwhelmingly cluttered, and it's pretty well-organized. The dressing rooms are a little shoddy, but I've seen worse! Customer service is average.
My favorite find at Savers: a beautiful shalwar kamise, found in the costume section!