Best CSS color wheel sites

Adobe's Kuler - http://kuler.adobe.com/

is widely considered to be the best color palette selector out there, as it also lets you share color palettes other users have created. Sign in, click create, and you'll have options including "complementary" that give you a good starting point if you have one color in mind.

http://www.colorschemer.com has an online color scheme gallery.

They also have a free desktop app called ColorPix:

                                          
_{(source: colorschemer.com)}