There are countless color-generating tools out there, but this tool from ColorJack recently caught my eye. Though it's not the most customizable, it is the only tool that I've seen that puts you in the shoes of about 10% of the male population - those that are color blind.
It was very interesting to see how the palette changed when it was simulated for the most common red-green deficiencies (deuteranopia and deuteranomaly). My misconception was that this deficiency only affected reds and greens, making them a sickly brown, but it actually affects all the colors (which I should have known...red and green are in all sorts of colors...silly me).
The usability would be even greater if you could input your color scheme and see how it's affected, but alas, this is not so. But play around with it...it will give you an interesting perspective!
