A year or so ago a friend of mine told me about this little app called Synergy. It is an open source utility which allows you to use a single KB/mouse to manage multiple PCs. It is a very slick little tool that works on linux, windows, and OS X.
It is a client-server setup. The server is the PC which has the keyboard and mouse attached to it. The client is a very small agent running on each PC. Configuration for the client is simply providing the DNS name or IP of the server. The server config is a just a hair more involved. You have to tell it which clients are connecting to it and how they relate to each other for mouse movement.
The behaviour acts like you have multiple monitors. Simple move the mouse to the edge of the screen you have defined in the layout and it starts moving on the other PC. I don’t see any limitations to the number of PCs you can have connected, though I am sure there is a point where it would become cumbersome to move between all of the screens.
Of course Ubuntu Communities has nice documentation on how to configure it including for autostartup at various points.
no comment untill now