MacBook Pro and iMac dual monitor

Can I use my 24" 2008 iMac as a dual monitor to use with my 15" 2011 MacBook Pro? I have a friend who can hook his Acer laptop up to his Acer monitor and can drag windows between the two screens. I was just wondering if there was a way to do something similar with my current models of Macs. Any help would be great!

-Geoff