We researched several different options for doing this, and here's what we found: Ideapaint looks awesome, but their $175 price tag ... not so much. http://www.ideapaint.com/ Krylon apparently makes whiteboard paint much cheaper, but reading the reviews made us a little wary of how well it would work.
We decided to paint our desktops white and then use several coats of polyurethane to create a clean-able surface. After a few coats, though, the brushstrokes were just a little rough and it didn't seem like it would hold up, so we abandoned that idea. (Don't worry, our desks are really cheap IKEA!)
After doing a little bit more research, we learned of a product available at our local hardware store called "showerboard." I guess the original and intended use is for lining showers, but it's white and waterproof which makes it the perfect whiteboard material! It's basically masonite with a white side. We had Lowe's cut the showerboard to the exact size of our desks, brought it home, put it on the desk and viola! We had a whiteboard desk!
I thought that we would have to put adhesive on the bottom to make it stay in place, but with the large size and heavy monitors and computers it hasn't moved at all. The edge isn't completely clean and perfect, but it's not bad as you can see in the photos. I use Wet Erase markers because they tend to be less smudge-able and I just have to use a hand wipe to clean it off, but Matt prefers dry-erase.
So, lbobians ... BE INSPIRED! Get rid of the sticky note mess!