SwitchResX is a tool designed to manage resolutions of all your monitors. Here's a quick summary:

• As standard features: it gives you access to most of your monitor settings within its customizable menus (in the Menu Bar or on the Finder Desktop with a Contextual Menu Plugin). SwitchResX incorporates features relative to the Monitor Resolution, Color Depth, Video Mirroring, Display Rotation into one single utility.
• An other useful feature: it lets save positions of the icons on the desktop, positions of the Finder windows, and restore them automatically when the resolution is changed.
• Specialized features allow you to link your monitor settings with system events: Key shortcut pressed, Apple Scripts, Application launched.
• Advanced features lets you enable more resolutions, or even create new resolutions for your monitor, HDTV, Plasma screen or Video Projector. This advanced feature is very powerful for users requesting complete control over their display resolution.