Update Notifier is a standalone application that checks what software apps you have installed, and informs you if there are updates available for them.
As most of us have loads of applications installed, and many don't feature automatic updates, Update Notifier is quite a useful tool. It doesn't require installation, and can be run from a USB drive, so can be part of your portable toolkit.
While it's a neat system, it isn't flawless. When you click the download updates button it automatically opens a link through Microsoft Internet Explorer, and you can't define another browser. Its database isn't comprehensive either, so it's possible you'll have programs it doesn't cover. Registered users can submit programs to update, but it's really aimed at developers, and quite complex. It's a shame there's no auto-update, or multi-update option - you have to update programs one by one at the moment.
Update Notifier is a helpful little application that will keep you up to date with most of your popular programs.