Dribbble Color is a wonderful tool that allows you to display all dribbble shots, based on a certain color.
A very useful free color wheel and color palette generator for designers and developers. You can also upload an image to get colors from it.
Color Hunt is a free and open platform for color inspiration with thousands of trendy hand-picked color palettes.
uiGradients is a community contributed collection of beautiful multi-color gradients, free to use on your next UI or design project.