A new xPL application is available, for some weeks now; xPL Updater. The application lists all applications known by the different vendor/developers from their plugins.
If you’re looking for a start in xPL, check the list in this application. For each app you can find the details on versions, vendor, info-webpage and download webpage. It also maintains a list of versions, and shows new/updated versions with an icon indicator. As for all developers; please check the application for your own apps and update your plugins if required (see the updated plugin spec).
The application itself runs on Windows, but lists all applications for all platforms (from the downloaded plugins) and checks the versions of all local applications (seen on the network and on the local windows machine) against the latest version.
You can download it here.