I like to keep my system up to date and the Mac App Store is great in that it automatically notifies you when updates are available for apps downloaded from it. However, I'm after an easy way to get notified of updates for all of my apps not downloaded from the Mac App Store. I'm talking about things like Skype, Spotify, Firefox etc. without having to go and start up each app first and let it do its own update check.
I've seen sites like OldVersion and OldApps which do have information about the latest versions of apps and their release dates, which could potentially be "scraped" to obtain this information, but they don't seem to be updated terribly regularly as far as I can tell.