If you played with a Meccano set when you were younger as I did this MicroRAX mini T-Slot Construction system may bring back some of those construction ideas. I have seen a larger version of this system used in industry for constructing modular systems that are very rigid and simply to modify. It looks like it could be an ideal solution to building a robot platform where the end result is more of an evolution than a set construction plan.

Update. I forgot to mention that MicroRAX is giving away some free samples, this will allow you to have a look at the product before you buy. The free sample is probably time limited so act now, pass this along to your mechanical engineering friends so that they can learn about this product also.

Via: Hacked Gadgets Forum

"MicroRAX a light weight miniature T-Slot building kit. Suitable for use on your desktop or bench top to build science, engineering, or advanced hobby and DIY projects. This small rugged framing system is ideal for use in machines, school science projects, robotics, design houses, workshops, prototypes, repair, models, gadgets, maintenance, etc."