the cheap kind, not the interactive fancy ones.
For conceptual work:
http://fnoschese.wordpress.com/2010/08/06/the-2-interactive-whiteboard/
with videos
http://physicsed.buffalostate.edu/AZTEC/BP_WB/index.html
this has to be legit right?
finally this one, where you can purchase white boards:
http://home.comcast.net/~whiteboardsusa/whiteboardsusa/whiteboarding.htm
steelcase must have them since we use them in a classroom (click on the links in that post for more visuals)
called verb whiteboards for some reason