Antother option is SmartBargains.com. It's Loehmann's online. I just ordered three dresses to choose from for my office's Christmas party. Not a black tie event (thank god, since I'd never get my husband in a tux), but I needed (well, maybe "wanted") a new cocktail dress. They have gowns, long dresses, short ones, and usually at a good price.
Hope you find something great, no matter where you get it!