Construction toys for you to 3d print: triangles and pentagons that snap together. Includes OpenScad source files.
Also available on Thingiverse: http://www.thingiverse.com/thing:92243
Examples in the photos were printed on a Makerbot Replicator 2. You might need to adjust the size of the snapping nubs if you're using a different printer or material.
Inspired by these things, but incompatible with them: