Oberling:
Is there any way that you could build a motor sheld?
Sure - if you know how to solder and read (or make) a schematic, you can easily build an L293 (SN754410) based h-bridge "shield" on a piece of perfboard; building an L298-based shield on a regular piece of perfboard, though, is -almost- impossible (the pins of an L298 do not follow a 0.1 inch hole spacing pattern), but you can buy adaptor PCBs to allow you do do it. Anything beyond that you would need to build using discrete components (transistors/mosfets), which can (if you aren't experienced with design and construction of h-bridges) end up costing more (due to burning components out) that just purchasing an equivalent h-bridge.