Synergy, wow, this is one of the most useful tools I've found in a while. It's a software KVM basically. A single PC's keyboard and mouse can be shared between many machines. In addition it runs on many operating systems including Linux and Windows. At the moment I have it set up to use my desktop Linux box's keyboard and mouse on my Windows Media Center laptop. The Synergy web site is here.
To use it on Linux as a server you need to configure a .synergy.conf file in your home directory. I've given mine here, it's pretty small and does the min, but it works great.
left = windows-laptop
right = linux-box