I found this neato color tool, and I really like the color tester option which lets you see the palette in action.  I always stress over putting sites together for clients, especially when I have to choose colors, but this makes the job a lot easier.

http://www.colorcombos.com/

Nice, I like this one too. Server is a bit slow atm.
http://colorschemedesigner.com/

Ooooh ohh ohh ooh

OK, this "pull colors from a picture is wonderful.

http://www.degraeve.com/color-palette/index.php

How in the world do you have a script tell you if a color is "vibrant" or "dull"?

the one Drastic mentioned is my favorite... but also

http://www.colorschemer.com/online.html

Sometimes it's helpful to search this one with the RGB hex code (use palette search, not colour search) if you're looking for a scheme that goes well with a given color (esp. if you're color blind like me and need mechanized and human help)

http://www.colourlovers.com/

Given above-mentioend colorblindness, I think the "pull colors from picture" could come in quite useful for me!

http://colorblender.com/

as well.

(start playing with the sliders)

But I probably use Color Scheme Designer most.

Ergo - thanks for the tip for colourblindies.  Nice.  I'm CP2 which is seemingly quite bad - not allowed to fly as P-I-C from 1 hour before dusk and 1 hour after dawn.