As someone that had quite an extensive lab set up at home, this application is a lifesaver. Synergy basically allows you to control multiple machines using the same keyboard or mouse–even across multiple OSs. The main difference between Synergy and a KVM is the “V”. Synergy assumes you use different monitors. I would typically have 3-4 monitors on so I could see multiple views at once. Plus, the clipboard share is a huge timesaver.
From the Synergy website:
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. Learn more about how it works.