Use your laptop as a monitor for another PC

MaxiVista turns any spare Desktop, Laptop or Netbook PC into a dual monitor for your primary computer. No extra multi monitor hardware is required. Simply extend program windows across multiple screens as if it were one big monitor. Increase your productivity by using multiple monitors.

Control up to four computers from a single keyboard and mouse even more convenient than using a KVM switch - Simply move the mouse cursor to the computer you would like to control with the software KVM feature. Save yourself from juggling multiple mice and keyboards. No need to buy expensive kvm switches.

The Clipboard Sharing feature transfers the clipboard data amongst all computers. Whatever you copy to the clipboard of one PC becomes available in all other computer's clipboards as well. Synchronizing the Clipboard has never been so easy.

(From their website)