Kuler
Adobe Kuler is a Flash-based website that allows you to interactively select colour palettes. I've found that it's handy for clients that want to change colours on a design because you can direct them to this site and have them make the selections. This prevents the back-and-forwards between our design team and the client.
Check it out.
Here is another that apparently Adobe ripped off :) http://www.colourlovers.com/
ColourLovers isnt the same its more of a place where people post their colour swatches. Adobe’s has similar but it has the ability to create your own with the colour wheel.
http://www.colorjack.com/studio is also another place.
I prefer the Adobe one myself its easier for clients to poke around and get a better idea.
Its Pixelicious!