Icehouse is a board gaming system (like a deck of cards) with a dedicated community of fans. There are 3 types of pyramids: small, medium, and large. a set of 3 pyramids is called a "nest", and a set of 5 nests is called a "stash".
Icehouse pyramids can be used to play any of the 300+ games found at http://www.icehousegames.org. Many games can be played with only one stash, but with 5 stashes (and a few odds and ends like playing cards and dice) you can play almost every game on the site. The coolest part about Icehouse is the community that has been built around inventing and sharing games. Sadly it seems to be stagnating a bit lately, so maybe the thingiverse community can help revitalize things?
I designed these in sketchup using the official specifications found here: http://www.wunderland.com/icehouse/MakingIcehouse.html
I originally meant to print these in batches of 6 pyramids (2 nests per print), but have found that this results in ugly and misshapen pyramids. While the results are usable, I'd recommend printing them out one pyramid at a time to make sure you have good looking nest that fits together well.
I have included an stl file for printing either one or two stashes in one print if you're in a hurry though. I'd be interested to hear if anyone prints a good looking set, since I might just have skeinforge set up wrong.