A KVM switch (Keyboard-Video-Mouse) is a major boon to anyone who has to work with more than one computer. You can change computers without having to give up the keyboard and monitor you're already using, sometimes via the keyboard itself. Imagine the space and money you'll save, only having to buy one monitor, keyboard, and mouse. 

After saying that, KVM switches stop being exciting pretty quickly, so let's look at things to shop for. Will it switch your speakers, too? How about your microphone? Is it USB only, or can it handle older connections? Hardware button, keyboard command control, or both? Does it draw its power from the computer, or does it need a power adapter? How many computers do you need to switch? (Most KVM switches will handle two computers; some can handle more.) 

The DLINK KVM-121 2-port PS/2 KVM switch manages two computers using only one monitor, keyboard, and mouse. With the built-in audio support you can share a set of speakers between two computers. The KVM-221 is easy to install and use - no drivers or software is required. Is this the switch for you? Check it out and see!