Synergy: Share your mouse and keyboard across different operating systems

Synergy lets you share mouse and keyboard across multiple monitors even with different operating systems!

For step-by-step instructions follow this link http://www.mattcutts.com/blog/how-to-configure-synergy-in-six-steps
This site specifically mentions Ubuntu distro but you can download the source from here and install using the typical linux commands
./configure
make
sudo make install

The above page uses Linux as server. Initially I tried setting up Windows as a server using this link
But the GUI wasn't intuitive and faced some networking issues so switched to Linux instead.

In the synergy.conf file under the aliases section you can specify IP address of the screen. Each screen can have multiple aliases; 1 per line (no colon).
The synergys (server daemon) uses gethostname() so if you've specified screen name that is different than the hostname then use -n server_screen_name while starting the synergys.

For more troubleshooting information refer here

If you are using KVM then make sure that the respective monitors are directly connected to the VGA port and not to the KVM switch!!

Work seamlessly. Enjoy!