Maintaining 1:1 rendering on high res screen (Snow Leopard)
Go to System Preferences (the square gray icon with gears on it) in the Dock and choose Displays, then select the resolution from the scrolling list of possibilities.  You should certainly be able to set 1920x1080, though of course there will be wide black bands around the output.

Generally, on OS X, unlike Windows, video hardware manufacturers do not install their own control panels or preference apps.