Color Hunt is a free and open platform for color inspiration with thousands of trendy hand-picked color palettes.
Gradient by ShopFactory is a great tool for finding wonderful gradients, to use in your next project. It allows you to control the gradients based on different settings.
Color palettes generator, ColorSpace is a space for everything that has to do with color palettes and gradients.
Dribbble Color is a wonderful tool that allows you to display all dribbble shots, based on certain colors.