A Scaleable Color Picker – colorjoe
colorjoe is a new one which differentiates itself by being completely scaleable which is great for responsive layouts.
It doesn't use any images, can be customized with CSS and works with all major formats (RGB, HSL, HSV or CMYK).
The color picker is standalone and has 2 callbacks:
change (which is triggered continuously to detect value changes) and
done (which is fired when a color is selected).