I just found this on Monoprice: http://www.monoprice.com/Product?c_id=104&cp_id=10423&cs_id=1042302&p_id=2946&seq=1&format=2
It's a 3-way optical switch, which should let you switch your input from PS3 to PC with the flip of a switch. You won't be able to listen to both simultaneously, but I don't think that's what you were asking.
I may use this to setup my system like this:
Xbox->Switch->Recon->AVR (for Amping)->Headphones
This lets me use the AVR as a headphone amp to boost the output of the Recon, while easily letting me use it for regular speakers as well. My current setup will let me use the AVR and the Recon at the same time, but the AVR comes before the Recon so I can't use it to amp.
Actually I think Hedonism was wanting both to play together. Chicolom owns this puppy and I recall him saying that it can have multiple sources active simultaneously, allowing for a mix of the two/three/four. Downside is that it's RCA and 1/8" only, so you'll need to have the right connections for it.