Just bought some nice big 2'x3' whiteboards from Lowe's to use for a "reMARK-able" line follower track for Maker Faire. They're $7, marked down from $10. Thicker than most at 0.193", nice & stiff. Could make a standalone table by adding two ribs, some legs, and an extruded edge guard. Good for robot clubs, scouts, schools, etc.
Alternatively, you could also use them as whiteboards.
Matt Gilliland made several gorgeous big display/play tables for the 2012 Parallax Robot expo, this material would be perfect for the 2018 event. Are we still on track for that, Ken? When izzit? Got hats?