Just thought I'd point out that for smaller robots and parts, you can pick up kitchen cutting boards made of HDPE from Wal Mart, KMart, Target, etc. I bought one at Big Lots today for $3. 8" x 12" x 1/4". It was either that or order online (couldn't find any locally for a reasonable price) for $6 per sq. ft. or so, plus shipping.
FYI...