When you see the word Arc next to Microsoft you usually think of their sleek portable mouse with the foldable curved back.  This time though Microsoft has applied the name to their newly introduced keyboard.  The Arc keyboard has an arch along the spine of the keyboard for more comfortable ergonomics along with a weight of less than a pound.  It connects to your Mac or PC via a tiny USB dongle.  The keyboard will be on sale February 21st, 2010 for $59.95