Kuler is best used inside Photoshop and Illustrator. To those who don't know, it's natively supported (see: Window->Extensions->Kuler).
http://www.colourlovers.com/ is another good one, though somewhat bloated.
http://www.colourlovers.com/ is another good one, though somewhat bloated.
I am completely unable to coordinate colors. And algorithms (``on the color wheel take 12 o'clock, and 5 and 7'') are very limited. What I find useful is a site where people who are into this kind of thing contribute their work and I use it, with grateful acknowledgement.