Although an avid Internet Explorer user, other internet browsers have their shining moments. There is an add-on available in Mozilla Firefox named ColorZilla that had me very excitable yesterday. (Thanks Sean!)
This colour picker tool allows you to use an eyedropper to get a colour reading from any point within your browser.
Free. Two second download. Restart browser to install.
You can always find the latest version at http://colorzilla.com/