Control all your PCs from a single PC
You can do this with Keyboard/Video/Mouse (KVM) switches, or with VNC, but here's an even more efficient and elegant solution...
This neat open-source utility from Synergy is worth a try: http://synergy2.sourceforge.net/
It works like a dream ... you tell it the physical layout of the screens connected to various PCs and then you can use a single mouse to move the pointer across all screens. You can then use the mouse as per normal on whatever screen/PC you have the mouse pointer on, and, when you're on a particular screen the single keyboard you're using will be fully active on that screen/PC as well. Plus you can copy/paste between PCs in a blink. I'm using it now from my instructor station to manage all 5 PCs and 6 screens in my flightdeck. Only 1 mouse, 1 keyboard, and no extra cabling needed.