I've recently found out Adobe Kuler. It's a free, flash based application for creating colour swatches. You can create your own themes and then share them over the kuler network. You can also search for tagged colours or analyze what tones are mostly chosen by people.
What's the best thing about it is "Create" function which displays a colour wheel with five different colours selected according to few rules which you can choose from. I've found that "Analogus" works best for creating realistic gradients of stones, grass or other natural elements.
You can copy colours with RGB, HSV, CMYK and even Lab values.
I highly recommend it --> http://kuler.adobe.com/
cool :)
been using this for a while...with mondrianum (mac only)( http://www.lithoglyph.com/mondrianum/ (http://www.lithoglyph.com/mondrianum/) ) you can use it from within tg and cs3 etc...it's pretty neat!
Corel Paint X2 has a very good palette editor. When the Windows Color Chooser won't cut it, I run Paint X2 and use its editor.