WikiHow has a simple method for removing permanent marker from dry erase boards:

Get the board you want the stuff off. Get a dry erase marker (yes, we will make marks to take marks) and a dry eraser. Draw over what you want to erase (make sure you draw slowly to fill it in better). Erase. Done!

I've actually used this method, and frankly - it's incredible! When I first learned about it, I was coloring my dry erase board with a Sharpie, letting it dry, then dry erase markering the Sharpie off for the sheer joy of it. This may be old hat for some of you, but when I first learned this there were a lot of dropped jaws in the room.


How to Erase Old Marks off a Dry Erase Board [wikiHow]