One thing that would always disappoint 7-year-old Brian (me) was the fact that no matter how hard I tried, I could never get all of my different construction sets to play nicely together.

Cry no more, all you children (maybe even some adults) out there. There is now a solution for all your incompatibility issues. Thanks to a project by F.A.T Lab and Sy-Lab, in which they have created numerous designs for what they call the Free Universal Construction Kit, it is now possible to interconnect 10 different types of construction sets.

The Free Universal Construction Kit is a matrix of about 80 different adapter bricks. The designs for each of these bricks are made available for free on Thingiverse in .STL file format. Once downloaded the bricks can be printed out on pretty much any FDM 3D printer.

http://fffff.at/free-universal-construction-kit/

Ever wanted to connect your Legos and Tinkertoys together? Now you can — and much more. Announcing the Free Universal Construction Kit: a set of adapters for complete interoperability between 10 popular construction toys.

The Free Universal Construction Kit offers adapters between Lego, Duplo, Fischertechnik, Gears! Gears! Gears!, K’Nex, Krinkles (Bristle Blocks), Lincoln Logs, Tinkertoys, Zome, and Zoob. Our adapters can be downloaded from Thingiverse.com and other sharing sites as a set of 3D models in .STL format, suitable for reproduction by personal manufacturing devices like the Makerbot (an inexpensive, open-source 3D printer).