I have a laptop at work and convinced my boss that i needed a bigger monitor to connect to the laptop, as the bigger space will make me more productive :-) He bought it!
Extending my 15" laptop desktop to include the 19" monitor gave me a much bigger space to work on and ive become so used to it that i get frustrated when im limited to only the laptop screen when not in the office. Anyway, i have a second older laptop at work, my old one, which was just sitting there gathering dust, so i started using it as well.
It was only last week that i found this awesome software that i realised how much fun i can have if i can control all three screens (current 2 extended screens and one more pc accessible via a network connection) with ONE keyboard and ONE mouse.
Synergy allows you to setup a server and client PC on a network, one sharing the other using the shared mouse and keyboard. The the client will have the server's mouse and keyboard movements sent via the network and you wont even see or feel the difference, its like having the periferals plugged directly into this pc even if they arent :-)
I now have a desktop that spans 3 monitors, one dedicated as an internet browser, one dedicated as an email manager and the last my main monitor for my other tasks.
My original request for an additional screen to my boss was not really for increased productivity, but now that i have three i can assure you the setup is making me less distracted from the important things that are always in view on the other screens and not hidden behind other application screens.
Download Synergy from http://synergy2.sourceforge.net/