This is my favorite stop for "new" work clothes!! They have a good, varied selection of slacks, work tops, jackets and skirts - as well as some cute casual items. The prices here are fantastic - last time I went to got 3 items (Anthropologie, Esprit and Lucky Brand!) for $33. The clothes are always in good condition and often still have their dry cleaning tags on them.
As is the case with second hand places, it can be hit or miss but that makes it okay to shop there every week! I've never sold anything to them so I cannot comment on what that process is like.