check out shopbop : http://www.shopbop.com/
(there are a bunch of cute dresses in the 70% off section right now too)
also, american apparel always has good basic dresses/fun shit: http://store.americanapparel.net/women-dresses.html
gilt is aight but you have to request membership which takes a minute (at least you used to?)...also its hit or miss depending on what designers they're selling, but worth a try.