jerettk:
Hi,which 5V are you talking about? if you are referring to the 5V that is labelled on the board. if I am not wrong, those are actually 5V out.
The shield 5V pin is actually wired directly to the boards +5vdc Vcc bus. So while the arduino designed it to provide +5vdc output voltage to power external components, it's quite possible to power the board by wiring a regulated +5vdc to this pin and ground, and many people do and have. There is the issue I raised below, but again it's not something that isn't done successfully by many in their projects.
LeftyWhat people usually do is to power the their arduino using USB or through an ac-dc power adapter (3.5mm) type?