Just found this, and thought I'd share it with everyone:

As designers, we sometimes forget that not everyone can see color the same way we do. I found a sweet app that allows you to simulate what color blindness does to your designs, whether it be interface design or the composition of a 4-color poster.

Here's an example of this page as viewed by someone with color blindness:

So this free app for Windows, Linux and Mac simulates how approximately 5% of all men will see your designs. It's a pretty cool app to add to your toolbox o' design stuff.

Anyway, the app is here http://colororacle.cartography.ch/