[pdpi]

First thing I thought was that having both my PC and my Mac Mini on the same keyboard would be cool (and this is a fair bit cleaner than a KVM)

[ChrisClark]

Check out http://synergy-project.org/ you can share your keyboard and mouse between the computers. Just move your mouse to a screen edge and it jumps over to the other computer.

I use it for work, OSX on my left Windows on my right, single keyboard and mouse. It will even let you copy-paste text between computers.