I have my PC in a closet. I have long cables that run from the components (keyboard, monitor, mouse, audio interface, and an empty USB cable for thumbdrives), through a PVC pipe in the wall into the closet. Pipe needs to have some kind of curve or bend in it to be really effective.
It doesn't get terribly hot in there, but if it did I could just vent it out the other side if need be (it backs up to another closet). I got tired of having to open the closet to turn the PC on so I mounted a power button to my desk and used a long enough wire to the power jumpers on the motherboard.
Of course, if you don't own your house or you don't want to cut holes in your walls then this won't work for you.