A lego-like kit that depicts the Chernobyl reactor facility before and after it melted down in 1986.
Custom LEGO minifigs!
A LEGO version of HAL 9000, from the movie 2001: A Space Odyssey. All of the red and yellow parts can be replaced with any colour, without changing the outward appearance of the model.
The black bricks are where the LED bricks are supposed to go.
The Universal Construction Kit is a set of open source components that you can fab on a 3D printer, which allows the user to hook together different construction kits without duct tape or twist-ties. The components make it possible to use Lego, Duplo, K'Nex, Lincoln Logs, and other construction kits in the same project simultaneously.
The whole set can be downloaded as a .zip file from the website.
The .stl files carry a Creative Commons By Attribution/Noncommercial/Share Alike v3.0 license.
Note that the .stl files are in inches, not mm. Double-check the settings of your 3D printer before fabbing!