I'm selling a Microsoft Natural Keyboard Pro that's in great condition. It retailed for $75. The one I have was distributed by Dell. The Pro is one of the best reviewed natural keyboards:

http://www.amazon.com/Microsoft-B61-00002-Natural-Keyboard-Pro/dp/B00002JXFH

Features:

• Design encourages natural hand, wrist, and forearm positions

• 19 hot keys, including ones for Internet, multimedia, and e-mail applications

• Launch your browser and surf the Web directly from your keyboard

• 2 USB ports let you easily plug USB devices directly into your keyboard

• IntelliType Pro Software lets you customize hot keys