Thanks again for your responses! I have a few more questions:
Motorshield works great via USB power or devoted arduino power. I am running one stepper motor, the stepper motor sold by Adafruit for $14. But when I try to plug my power supply directly into the motor shield (I removed the jumper and double checked the proper polarity), my stepper motor jitters out (does nothing but jitter). The power supply is a radio shack AC to DC adapter, 13.8v DC output with up to 3amps current (http://www.radioshack.com/product/index ... Id=2103959
). The stepper motor should only be taking in .6 amps/phase, so this power supply should have more than enough power.
Also, the FAQ say that the practical current limit is 2amps. Is that for the entire system, or per H-Bridge (meaning 4 amps total)? So I should get a power supply with more amperage if I am to run more powerful things?
With the wingshield you mentioned above, which should allow me to breakout my arduino pins onto a breadboard, what pins will (or will not) be available for me to use? Surely the motorshield will be using some of the pins.
And what would happen if I run a DC motor rated for higher voltage (say 12v) with the power of only 7.4v? Will that mean the amp draw of the motor also be lower?