You could probably mirror your display with VNC. <a href="http://en.wikipedia.org/wiki/Virtual_Network_Computing" rel="nofollow">http://en.wikipedia.org/wiki/Virtual_Network_Computing</a>
It would show the GM's view though, so no hidden surprises or fog of war without a second computer.
If you want to do it off a single computer, you'd probably be better off with either a long VGA cable from your laptop to the projector, or a wireless VGA solution like <a href="http://www.iogear.com/product/GUW2015VKIT/" rel="nofollow">http://www.iogear.com/product/GUW2015VKIT/</a> so you could set the projector up as a second monitor.
Then, run a second instance of the browser (Either in incognito mode, or one on Firefox one on Chrome) and have that connected as a "player"