GUI front end for Synergy2 "software kvm".
A little background: Synergy allows you to control two computers (each with its own display) using 1 set of keyboard and mouse without buying additional hardware.
Best thing is that Synergy runs on OSX, linux and Windows, so you can run two different OSes on two screens side by side.
Unlike traditional KVM, you don't need to hit a button to switch from one system to another, Synergy lets you control the other screen by simply mousing over to it.