I mentioned Synergy in September 2004. However, I should mention it again because of another program brought to my attention in the forums.
Desktop Rover – $48/2 licenses
Control all the computers (and Pocket PCs) on your desk with one keyboard and mouse. You can copy and paste between computers as well.
However, you need a license for each computer!
A license must be purchased for each computer. A single license allows you to install the software on a single computer and one Pocket PC device as described in the license agreement.
Synergy – open source software (free!)
Synergy lets you easily share a single mouse and keyboard between multiple computers with different operating systems, each with its own display, without special hardware. It’s intended for users with multiple computers on their desk since each system uses its own monitor(s).
Redirecting the mouse and keyboard is as simple as moving the mouse off the edge of your screen. Synergy also merges the clipboards of all the systems into one, allowing cut-and-paste between systems. Furthermore, it synchronizes screen savers so they all start and stop together and, if screen locking is enabled, only one screen requires a password to unlock them all.
Thanks to Brian Gaut for bringing up that other program. I hope Synergy does the trick for you and saved you that money!