This is a basic question but I can't find the answer. Am I going to fry anything if I plug in USB and a 7.4V LiPo battery (in Vin/GND) at the same time? The board is the Uno R2. Thanks!
Nope, you'll be fine. The Uno will use the LiPo battery source over the USB in this case.
-- The Rugged Audio Shield: Line In, Mic In, Headphone Out, microSD socket, potentiometer, play/record WAV files