Colormind uses 'deep learning' to generate different colour palettes and schemes.
Coolors.io is a colour scheme generator that allows you to both create, and explore, a range of palettes.
A very useful and speedy resource for quickly finding beautiful gradients. Also gives hex codes and full screen preview.
Adobe Color, formerly Kuler, is such a powerful tool for both discovering and creating colour palettes that compliment, contrast or compound.