Most of the clothing on the following sites come with a price; however, there are some beautiful clothes on all of them (IMO). I've used several of these just to get ideas for other outfits.
http://www.yosa.com/
Those that know me, know that this would have to be one of my favorite sites. The dresses are just gorgeous but incredibly expensive.
http://www.galleryserpentine.com/
They have some beautiful clothing designs and corsets. The PVC bustle skirt has to be my favorite from that one though.
http://www.babyssb.co.jp/
I don't really fit the Japanese Lolita style, but this site has got some great clothing for it. The whole site is in Japanese, so if you can't translate it, the pictures are still worth a look.
http://www.corinthias.net/
They have some beautiful victorian clothing on this site.
And Frostmourne already mentioned another one I love.
http://www.amfkorsets.com/
There are some great corsets for the cyber look on there.
And of course for my platform boot fetish, there is always the popular
http://www.pennangalan.co.uk/
As easy as I break the heels on shoes, I could never bring myself to purchase a pair of those, but they are wonderful to look at.
I'm not wicked. I'm just viciously mischievous.