Use laptop monitor as an extra monitor?

http://www.magneticweb.net/twomonitors.htm

http://www.mediashout.com/manual2/

 

http://www.maxivista.com/

$49 , it works perfectly,plus if you already have a dual ,triple...monitor card on your primary PC you can add another monitor using your laptop or another PC.
There's a demo available with the only limitation of a banner at the bottom of the secondary monitor, so you can see how smoothly it works (no affiliation here)
(vote 10)