colpick is a simple Photoshop-style color picker jQuery plugin with RGB, HSB and HEX fields. Its interface is familiar for most users and it's also very lightweight loading to the browser.
colpick - Features:
No images! Just a JS and a CSS file
Very intuitive Photoshop-like interface
Light and dark easy-to-customize CSS3 skins
28 KB total loaded by the browser
Works and looks nice even on IE7
Extremely easy to implement