My right shoulder had been hurting lately, due to the movement necessary to reach my trackpad. I was using a standard, wired Apple keyboard with the number pad on the right, and my Magic Trackpad was to the right of that, making me reach pretty far to access it.
So, I set out in search of a standalone number pad I could use with my Mac. While I don't work with numbers often, when I do my accounting, it's a pain to have to type numbers from the top row of the keyboard. I looked at a number of models - both wired and wireless - and found what seemed to be the best choice: Logitech's N305. This works with Logitech's Unifying Receiver, is fairly compact, and, according to Logitech, works for three years with a pair of batteries.
But the N305 does not support Macs. Fortunately, in reviews for the product on Amazon, a number of people posted a solution. Download the free KeyRemap4MacBook, a preference pane that lets you remap just about any key on your keyboard or number pad. There is a specific setting in this preference pane for the N305: in the Change KeyPad Key section, you check Logitech N305 hack. The number pad works perfectly, though the top three buttons, which have specific Windows functions (one launches Excel, another the calculator, and a third switches applications).
Mac OS X Hints