Correcting a long-standing oversight by Apple, AppCleaner completely removes unwanted programs from your Mac OS. Dragging applications to the Trash just isn't enough because almost every app installs various support files in several different places all over your computer.
AppCleaner is one of the best utilities around to help you track down and delete these files. It provides a slick, 3D interface and two options for deletion: you can either drag and drop applications onto AppCleaner's main window, or you can have AppCleaner list potential applications--and even widgets, plugins, and screensavers--to uninstall. The program will then show you all the related files for any app you're uninstalling and ask which you want to delete.
You can set AppCleaner to "protect" certain applications from accidentally getting trashed, too, by manually specifying them or just by auto-protecting all default and currently running apps. AppCleaner also comes with a SmartDelete option that detects when apps are trashed and offers to remove the related files, making it great for cleaning up past messes as well as preventing future ones.