One of the things I find hardest to do, is produce a color palette for a designed piece. I can usually think of 1 color I want to use, but the trick is finding a range of hues plus another complimentary color, it becomes too much for me to just pull out of my brain on that color picking wheel. A lot of times I end up using the blah colors that are in my design program by default: boring!
To help with this problem, someone at work showed me this amazing tool! It has some flaws, (can't get the color gray in the mix, you're limited as to how many colors and variations you can get) but all in all, its an excellent jumping off point! Plus you can export your color selections into a Photoshop palette, genius and saves so much transcribing of RGB values! I'm really enjoying it.
Check out how it works here.