For doing prototyping on small embedded projects that require physical motion, what hardware prototyping tools are available? For my projects, I tend to spend more time finding parts (i.e. wood, aluminum, etc.) and making the proper cuts, measurements, and connections than writing the software and configuring the electrical hardware.

Are there any affordable products that will enable me to create physical hardware that is strong enough to support motion? If not, what techniques or tools are available to help develop the physical hardware more quickly?

Currently, I typically build my projects from wood and plastic scraps that I have lying around. What types of materials enable you to prototype more quickly?

CLARIFICATION: By motion, I mean something that has to bear stress like a robot arm powered by a servo motor and could handle moving or carrying 1-2 lbs.