As someone who has multiple computers and a rather large home and office network system, a while back I decided to try and consolidate and hook up two completely separate computers to a single monitor, keyboard, and mouse. For this, I picked up a Trendnet TK-207 2 port USB KVM switch. This switch allows me to hook up a single USB keyboard and mouse, as well as a standard VGA connected monitor, to two separate computers and, theoretically, switch between them as needed with nothing more than a simple click of a button, or by pressing a specific keyboard key combination.
Trendnet KVM Switch
Setting up the switch was easy. All you have to do is hook the included cables (video, keyboard, and mouse) to both computers, and then hook your existing keyboard, mouse, and monitor to the input ports on the device. After that, boot up both computer's, and you're good to go.
While this KVM switch is decent for the price, it does have a couple of negative aspects. First, the design of the switch is awkward, with cables coming out of all sides, rather than coming neatly out of the back. Second, switching between devices does not always go smoothly. In fact, sometimes it doesn't switch at all, but trying again usually fixes it. Overall, this is a great device if you need to hook up two computers to a single keyboard, mouse, and monitor.