[Eric Hunting] has compiled a list of these modular building systems. As the well-known XKCD comic likes to point out, the issue with standards is that they tend to proliferate instead of getting ...

To help address this challenge, [Nikodem Bartnik] is working on the Open Robotic Platform (ORP), a modular robotics chassis ... plates featuring a 20 mm grid pattern of 3.5 mm mounting holes.