Yeah, some serious keyword stuffing in the title there. I can't believe I've only just found this little tool. It lets you select the RGB colour values for any pixel on screen by dragging from the system tray. It can automatically copy to the clipboard and has multiple formats including HTML/CSS, VB hex, HSB.
That's the PC version. For real designers there's this one for the Mac (check out the page in a decent browser to see the nice, scrolling app icons at the top):