This thrift store probably tops my list right now for good finds in Pittsburgh. It is a bit out of the way (in West Mifflin) but if you are doing a lot of shopping, then this is the place to hit. (It is also close to Big Lots, Burlington Coat Factory, and a Gabriel Brothers).
Garments are usually well organized by type of clothes, and it doesn't overtly smell like mothballs. The clothes are also organized by color which saves me a lot of time when I'm hunting for something. Sometimes it can be a little on the pricey side (for a thrift store), and they are very strict about not selling something without a tag, so don't even try. Also, sometimes when they staple on the tags, they damage the clothes. This is a huge store, very clean, and a neat little staging area for the furniture.
Open 9a-9p Monday-Saturday.