One more to add for consideration: electrostatic sheets. You can get a whole roll of them for just a few bucks and turn your entire office into a whiteboard. No hanging, no mess. Surprisingly effective as a low-cost whiteboard-like solution.

And if you're sharing that whiteboard (in any form) with remote colleagues, try sharetheboard.com. Our team put it together precisely because we didn't want to say goodbye to the ol' board.