Synergy is an open source project and it runs on Windows, Mac and Linux. The most common use would be someone with a laptop and desktop computer. Come home from work/collage with you laptop and then work on it using the keyboard and mouse of the desktop computer. It requires software running on each machine and a network connection. It would be useful to anyone working in a mixed environment. Or hobbyists like myself to much about with. Many gamers will run a second computer along side their gaming rig for server admin and the like.
It really is like running a dual monitor setup, I have somethings running on one screen and others running on the other screen. It's working well so far I just need to do some work on the Linuxbox. I have not yet figured out how to have it correctly configured automatically on boot up so at the mo I need to have the keyboard and mouse connected. I need to do some more reading. I'm not sure where today has gone it feels like only a few hours since I got up... I'll look at it tomorrow.