AppHider

Drag and drop an application to AppHider and the app will be "hidden" from the Finder. Why, you may ask, would you want to do that?

Well, let's say you have two versions of the same app and you want the Finder to temporarily use the older version when launching documents. Just drag the newer app to AppHider and it will be hidden from the Finder. (Popular with Word 6.0 / 5.1 users. Another suggestion: With the arrival of QuickTime 3.0 and the limited version of MoviePlayer, use AppHider to hide the crippled version and use the old MoviePlayer 2.5.1, double clicking a movie will launch the older version.)