Rue La La

Rue La La (<-- it's a private, referral only site, so join through my link) is a great site. They host many "boutiques" each week of top name brands (think Theory, Tumbuk2, Sorel, Illy, Guess, Reebok, Calvin Klein, etc.).  I've bought a few items from them at majorly reduced prices (usually at least 50% off). You have to be quick, though, because their items sell out fast (that's because the deals are so awesome).