Wasn't sure if I should put there here or Urban Commandos.  So I'll try here.

Is there a danger in using a three-way splitter to attach the audio outputs of three PCs to one input channel on a receiver?  

I don't want to use a switch, and I don't want to have to separately select each PC as I want to hear it.... I want to turn on a receiver and have the sounds from all machines play through the same set of speakers.

My main concern is if the signal output from one PC would enter the output stage of another PC and risk damaging components that way.  I know they're low power outputs, but similar to how a diode allows for one-way electron flow, I'm wondering if something like that would be needed here.

Thanks.

Best way is to just get a small mixer.  That way you don't have to worry about back feeding the other audio boards.

... probably won't hurt anything, but you never know.