i'm planning on running my USB miners plugged straight into my litecoin mining rig (2 front mounted USB ports (2 miners ordered) - although i'm concerned about power - should i get a powered USB hub? i have also got a raspberry Pi that i have thought about using too - any recommendations?)
I think your PC will have enough power to supply juice to the USB ports for the miners.
With your Raspi you'll need a powered hub for sure. IIRC the Raspi only supplies 100mA to the USB ports (in total?).
You can get 500mA per hub, so if the two USB ports on the front are off separate hubs, you would be OK (except for the 100mA used by each hub...)
http://en.wikipedia.org/wiki/USB_hub#PowerFor the price of a powered hub (A fraction of 2BTC), I got one anyway, and added a 4A PSU.