Cheap DIY whiteboard substitute for teams on budget

Even cheaper solution: $15 at Home Depot gets you 4'x8' showerboard. Which you can write on with dry erase markers. You have to be a little more meticulous about cleaning than a true white board, but it is definitely cheap.

Ex: http://www.homedepot.com/p/Unbranded-Thrifty-White-32-sq-ft-...

You can still cut it to size and put some frames on to get it to look "nice" too.