I recently setup a dedicated Linux machine next to my Windows machine. Rather than using a KVM switch or two keyboards and two mice, I searched for a solution that would allow me to share the same keyboard, mouse, and clipboard between the two machines.
Enter Synergy. While it appears that is no longer under active development, it still works great.
For my setup, my Windows machine is the host/server—meaning it's the one with the keyboard and mouse physically attached. The Linux machine was the guest/client. I wanted to have everything shared prior to user login on the Linux machine so as to avoid the need for the second keyboard at all.
Most of the articles I found online involved adding the "synergyc" process to "Startup Applications". The only problem with this was that it's post-login for Linux. This was unacceptable.
Then I found the solution—put the command in the Gnome Init script. The tutorials also talked about putting it in the PreSession startup script as well because, as they said, the synergyc process would get killed on login. I'm using Fedora 11 and I didn't find that to be the case.
Simply add the following to the /etc/gdm/Init/Default script, just above "sysmodmap=…" line:
The only other thing I had to do, after configuration and starting the process on the Windows host, was open a port on my Windows firewall.