Contraptor Project

Contraptor Parts

If you like Cartesian robots and/or erector sets, you should check out the Contraptor Project.  It's an open source construction set for things like CNC machines, plotters, and 3D printers.  It's kind of like a rapid prototyping system for automated construction/manipulation bots using cheap, easy to build parts.  Its components are easy to build with a few simple tools and they're compatible with their more expensive industrial counterparts.   Many of the parts utilize some interesting construction tricks so it's defiantly worth a look if you're into low cost robot construction.