Moshi's Zefyr is a portable cooling pad for the MacBook that provides a near silent fan, powered by USB, and offers a temperature drop of roughly 6 degrees C (12 degrees Fahrenheit). The Zefyr is designed to place your MacBook at an ergonomically beneficial tilt, and when not in use, the Zefyr collapses to better fit in a bag.
The Zefyr also provides a pass-through USB port, so that peripheral use is not sacrificed. A portable cooling pad might be a little silly, but for anyone who's experienced the heat of a MacBook on their lap, and worries about going sterile, it may be useful. It's available now in black and silver colors, and sells for $75. [Moshi]