For years I have been using the same old color picking tool. I don't recall the name, but it was very simple... Click on a button to "Grab Color From Screen", mouse over the color you need, click to lock it in, then cut and paste the #xxyyzz color into your style sheet.
After a recent upgrade to Vista x64, I decided to look for a new tool. A quick Google search led me to Iconico and their free color picker called ColorPic.
This latest generation color picker can store 16 different color captures as "chips", then save the chip collections for re-use later. ColorPic marks websafe colors (for those still concerned about supporting 1999 technology), and provides a Photoshop-esque mixer to tailor make a shade. The sampling region can be a single pixel or an average of 3x3 or 5x5 pixels; and you can collapse the sections you don't use to cut down on clutter.
The only drawback I see so far is that there are no "options". The default capture command is Control+G. If you would prefer another key combination or want to use a mouse click to capture instead, you're out of luck. Still, for a freebie, this handy tool provides a lot of functionality.