You should check the flash sales space for designer's stuff on the cheap: http://techcrunch.com/2010/09/13/ron-conways-confidential-in... -- there's more to it than Groupon :)
I've got some good stuff from Hautelook, Gilt and Ideeli, for me and my wife (strategically omitting the "el cheapo" part of the story, heh). You'll find a lot of minor brands there, then every once in a while a big-name-brand sale with stuff straight out of vogue or harper's bazaar.
Some of these are invite-only, but getting invites is not difficult, you just have to search around blogs and twitter. Here's a bunch of invitation links in case anyone wants to give them a spin (and just so you know, I'll get a referral bonus if anyone uses them + buys something there):
http://www.hautelook.com/invite/nprincigali762