uiGradients is a community contributed collection of beautiful multi-color gradients, free to use on your next UI or design project. You also have the ability to download the CSS gradient code.
Color Hunt is a free and open platform for color inspiration with thousands of trendy hand-picked color palettes.
Dribbble Color is a wonderful tool that allows you to display all dribbble shots, based on certain colors.
Color palettes generator, ColorSpace is a space for everything that has to do with color palettes and gradients.