Pixie is an easy-to-use, fast and tiny utility designed especially to fit the needs of Webmasters and Designers. Its a colour picker that includes a mouse tracker. Run it, simply point to a colour and it will tell you the hex, RGB, HTML, CMYK and HSV values of that colour. You can then use these values to reproduce the selected colour in your favorite programs. Pixie will also show the current x y position of your mouse pointer. Its the only tool you'll need for working with colours.
Pixie is the smallest, simplest, most functional colour picker I've seen to date.
HTML'ers and Photoshoppers should definitely try this one out.