Great site... have their "update checker" installed on all my computers and whenever there's a new version of any of the software they support, it will notify you and you can d/l the newest update..
another site is cleansofts.org They also have an update notifier you can download.
Between the 2 sites, pretty much keep everything you're running up to date.
You can also subscribe to a daily newsletter from versiontracker.com (cnet). They list everything they track that's been updated and you can scan the list to see if there's anything the others have missed.