TigerLaunch is an easy-to-use and easy-to-configure application launcher for OS X.
It displays an Apps menu at the top of your screen listing all your applications in alphabetical order - no matter what folder they appear in.
You can easily configure it to exclude applications you rarely or never launch.
TigerLaunch allows you to be more selective about what apps are dock-worthy, so your dock doesn't get so cluttered. It also makes it easier to launch apps that are buried in sub-folders, such as in the Utilities folder of your Applications folder.
The source code is available.