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