If you want to share a single mouse+keyboard with two (or even more) workstations, you can use x2x which has to be installed on every station – a ssh-server is also needed. Then you are able to connect the stations by
ssh -X username@remote_host -C "x2x -east -to :0"
After this command you are able to switch to the desktop of remote_host by simply moving your mouse outside the right side of your desktop. Choose the side by simply changing -east to -north, -south or -west.