DisplayLink has an application for the iPad that lets you use your iPad as a second monitor on a Windows PC. Wha? Yep you can use your Apple iPad as a second monitor for a Windows product, specifically XP, Vista, and 7. No need to run cables, this magic is accomplished wirelessly.
I use two monitors on my work computer and can never go back to using just one screen. The productivity gains with two monitors is amazing. Now I can do the same thing on my laptop at home, slick. This has to be one of the best iPad apps to date,