Mac's have supported multiple monitors since the release of the Macintosh II in 1987.

The primary improvement in the Mac II was Color QuickDraw in ROM, a color version of the graphics language which was the heart of the machine. Among the many innovations in Color QuickDraw were an ability to handle any display size, any color depth, and multiple monitors.

http://en.wikipedia....wiki/Macintosh_II

MacBooks don't have supported more than 1 external monitor - however, there is some technology from DisplayLink that will let you do it via USB.
http://www.displaylink.com

There are USB->DVI and USB->VGA adapters, as well as monitors and projectors that can be directly driven by USB.
http://www.displaylink.com/shop/

Mac drivers:
http://www.displayli...ac_downloads.html