I just discovered this really cool and free application that allows you to use a single keyboard and mouse across 2 machines.
In my case this is really useful home where I often have my personal desktop and my work laptop both on my desk. Having 2 sets of keyboards is quite cumbersome so this allows me to move the mouse from from one screen to another (the keyboard working on the machine where the mouse is) without having to either use the touch pad and laptop keyboard or going through a messy unplug-plug.
I tested it between my home XP machine and my work Vista one and it worked flawlessly (I’m actually typing this blog from my home keyboard on my work one ) but they also have Linux, Unix and Mac versions.
The only thing you need for this is a TCP/IP connection over a LAN.
Icing on the cake: it seemingly works with more than 2 machines too.
ps: I just copied-paste the URL from one machine to the other: It evens moves the clipboard from one to the other!