Now that Mountain Lion is out, developers are starting to roll out updates that'll make their apps compatible with Apple's latest OS. Users can easily keep up with all these changes using AppFresh for Mac. This utility from Metaquark will keep all your applications, widgets, preference panes and plugins on their latest version with minimal effort on your part.
AppFresh gets its update information from Apple's system updates, RSS-based Sparkle update and the repository of app updates maintained at the "i use this" website. It integrates into Growl notifications and will alert you when an update is installed.