Slate: Tiling window management for OS X
If you prefer something a little more simple, Spectacle is a free program similar to ShiftIt and SizeUp. Basically it's shortcuts to put windows in any half or quarter of your screen, centered, maximized, or send to other monitors.<p>On the app store: <a href="http://itunes.apple.com/us/app/spectacle/id487069743?mt=12" rel="nofollow">http://itunes.apple.com/us/app/spectacle/id487069743?mt=12</a><p>(I have no affiliation with this program. But I like it.)