I know of at least one temporary dry erase surface that works well. It's a 3M dry erase "sheet" that comes in rolls. You can buy it from American science and surplus: http://www.sciplus.com/search.cfm/scategory/SFM/term/whitebo...

I have a 6' x 10' surface of it on my bedroom wall, and it works great, even for erasing old marker.