zedin wrote:If I use the 5V pin off my pi would that be sufficient to run the relay board (or at least the LEDs)? Also is it ok to have a 5v line going to the raspberry pi's ground pin? Obviously it is not a straight shot from 5v to ground but goes through the components.
Powering a shift register and LEDs from 5V works (for about 8) if the LEDs are driven by the shift register.
To drive relays you WILL need an external PSU to drive the relays. Are you sure the shift register can drive the relays?
zedin wrote:And if I use an external 5v power source should I connect the two grounds together? Aka the ground from the Pi GPIO and the 5V ground.
GNDs should normally be connected between all sources (except where isolation is needed but that is more copmplicated). Without the GNDs tied together the voltage from the shift register will not drive the relays without the same GND reference.
Just another techie on the net - For GPIO boards see http:///www.facebook.com/pcservicesreading