Synergy
Synergy rocks !
It just works, cross distro, I have in the middle my laptop running an FC6, on my left the screen is connected to my RACK running a Xenhost on FC5 and on my right the iMac is humming on Ubuntu. I now have 3 screens at home and I`m only typing on 1 keyboard using 1 mouse. It took me no more than 10 minutes to download the appropriate pacakges (both FC and Ubuntu ship with Synergy in their Repo's ) configure it on 3 machines and start working with multiple heads at home.
Our cat really loves it.. she can now ly on the unplugged keyboard in fron to the screen while I type away on my main keyboard.