Colorate is a cool little tool that lets you analyze any image, save its corresponding image palette and create new ones. With 3 main palette tools (randomize, gradate, and blend) you can come up with all sorts of image palettes. These can be saved and listed on the left side of the interface or saved as .clr files to be used in any system palette.
All in all, Colorate feels extremely simple to use. The only real little nag I have with it is how small the hue, saturation and brightness controls are, making difficult to measure properly. Apart from that Colorate is great to quickly create your own color palettes.