App Update scans directories you specify for share- and freeware applications and looks for updates at Apple.com, MacUpdate and VersionTracker. It will produce a tidy list of updates with links to the download pages. App Update comes with plenty of features such as Growl support, ability to manage application versioning data, support for preference panes, quicktime plugins and frameworks, and more. It also has a built-in help function that you can access at any time by pressing "Shift+H".