Tracking Upstream Updates
It's not easy for maintainers to track when new upstream versions of ports are released.
Many projects, like FreeBSD itself, have some kind of announce mailing-list. You should subscribe to it and watch your inbox for new versions.
The list of unmaintained ports with an outstanding update may be of interest:
The service also sends out notifications via e-mail when updates are found. Contact Shaun or Martin to opt-in to this.
Repology, maintained by DmitryMarakasov, tracks package versions across a lot of repositories, including Linux (ALT, Arch, Debian, Ubuntu, Gentoo, Mageia, OpenSUSE, SlackBuilds) and other *BSDs (OpenBSD, NetBSD pkgsrc), compares versions and detects packages which need updates. Among other features, per-maintainer view is available:
See SourceForge, but the list is in the Summary section, not Files.
There's a page with recently updated modules. You'll have to watch it in order to stay current: http://search.cpan.org/recent
There should be a better way involving automated processing of the recent file against a list of CPAN modules you maintain. It will appear here later.
There exists a page listing available update at https://addons.mozilla.org/fr/firefox/search/?category=alerts-updates&type=extension .
Note: ATM legacy extensions aren't supported after Firefox 57.
Not clear yet
In the Files section of each project there's a list of packages named Latest File Releases, each with a monitor button to the right. Press the button to start tracking a particular package. You'll get a mail for each new release, but you won't get any notification if a new package appears in the project. Some projects release new versions as separate packages, making this monitor feature useless. You must be logged in in order to be able to subscribe.
Use other package management systems
You can track updates to separate ports at http://gentoo-portage.com/