App Update is a free Dashboard Widget that automatically checks for updates to your installed software. It supports Apple’s software directory, MacUpdate and Version Tracker. It will present you with a tidy link list of all the updates found, enabling you to read release-notes and download the updates you want quickly and painlessly.
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”.
You can specify the directories in which you keep your applications on App Update’s back (use the ‘i’ button to flip it over).
You’ll also be pleased to know that App Update is free, available right here.