i love shopping online. so much. it can get ridiculous. some faves are:
modcloth.com (especially for dresses)
karmaloop.com (takes time to browse so much stuff, but you can get good deals for sweet brands)
mooshoes.com
alternativeoutfitters.com
beyondtherack.com (fancy name-brand shiitake way cheap. kinda hit or miss depending on what's for sale. you need an invite to look though:
http://www.beyondtherack.com/member/invite/B39BA11Cbluefly.com (hit or miss also--often has matt & nat stuff, dresses, etc)
etsy.com (but sometimes i get overwhelmed)