Farm Show Magazine showcases a range of build your own ideas each month which have mostly agricultural intended uses. You can view a video now of a solar powered chicken tractor, firewood hauler, hand pushed sickle bar mower (soon to be for sale) and a pedal powered John Deere B. You can also quickly glimpse past issues using their index. Most of the ideas have crossover potential for other applications. A DVD collection is available and might prove to be a valuable starting point for pinpointing replicable solutions.
Design/Build Potential ??? I know that some university ag engineering programs engage students in real life design and build programs. Perhaps a list of candidate schools for such a venture could be compiled.