Synergy is software that does the Keyboard and Mouse part of KVM. The idea is that you have a bunch of computers, each with their own screen. But you want to use only one keyboard and mouse. Install Synergy server on the machine with the keyboard, and install Synergy clients on the other machines. Now all the screens act as a single unified desktop, and you switch where the input is going simply by moving the mouse off the edge of one screen onto another. And it works on multiple operating systems!
I haven't tried it, but it sounds damn handy.