TekRevue:

Apple has made it easy to keep your Mac up to date with the latest apps and patches. Once per week, the Mac App Store checks for any updates to Mac OS X and any App Store apps and notifies the user that an update is available. In recent versions of OS X, the Mac App Store can even install new updates for you automatically.

But sometimes one week is too long to wait for the newest features and latest security updates.

Great little tip for those of us who want/need to know about the latest updates as soon as possible.