Ever wanted to know what the color code was for that graphic on your monitor?
Trying to match the color of a logo you found a website?
Need to know the RGB value of that flower in a picture?
ColorPic is a cool little tool that I found today that lets you figure all that out. It has multiple "chips" (think of them as color slots) that you can use to grab colors and build a palette. It also includes a magnifier section so you see exactly what pixel you're grabbing. You can change the zoom level, and use the arrow keys to more accurately grab the exact pixel you want.
Once you've grabbed a color, it provides all the standard representations: Hex, Decimal, and RGB. You can then plug those in to just about any graphics program.
Also, because it lets you grab colors from your workspace, you don't have to download graphics from a website to load them into your graphics editor. It scrapes the values straight from your display, so if you can see it, you can grab the color from it.
It's not going to revolutionize the world, but when you really, really, really want to know what that color is, this will do the job for you.