Latest iteration of my open-source building toy. (Previous version here: http://www.thingiverse.com/thing:166730) The big new element with 3.0 is the addition of end hubs that make it easy to create structures built of tetrahedrons. These structures are essentially space frames and are very light and strong.

I've only included stl files for the basic parts but the SketchUp file contains lots of variations.

I'm very pleased with the capabilities provided by the new end hubs, and a little surprised that it took me this long to design that option.