Using laptop as third monitor? Best way to set up (without thunderbolt)? I currently  have a 27' iMac that uses a Samsung 16' monitor as a second display using Mini Display Port to VGA. I also have a 2011 Macbook Pro and was wondering if there was a way to set up this up as a third monitor to the iMac. The MDP is already in use, so what would be my options (if there are any) for connecting a laptop as another monitor? Also note that this monitor does not have thunderbolt, so thats out.

Thanks in advance for help.
Take a look at AirDisplay. It supports turning you Mac, Windows, iOS or Android into an external screen.

There are several other apps like this such as Screen Recycler, but AirDisplay is the one I currently use. 

Any of these apps will likely work best on a wired ethernet connection.