cPanel/Fantastico has a very cool feature that checks the version of installed applications against that which is currently available and alerts the administrator if an upgrade is recommended or required.
This type of application would be very valuable for a web company that installs open source software. Most of the time, each installation is the latest version, and when the project is done, maintenance is often forgotten or delayed.
Imagine a script like cPanel/Fantastico that could alert the company when an upgrade should be done.
It’s not that simple, though.
Open source is very easy to modify, and additional modules or plugins are often included. If an application has an active community, there can be hundreds or thousands of addins, which will all be maintained slightly differently.
There is no easy answer. However, if you set security as the primary goal (which you should), write a very simple script to get the application version strings from applications, and then use RSS feeds or other simple tools to check on the current status of the applications, as well as security reports/updates from the vendors, you should be able to track when upgrades need to be done.
Another approach would be to continuously monitor and upgrade applications with every version update. This would probably not be cost effective.
If you can run several sites through the same application installation, with separate databases, you may reduce the cost of maintenance, although the complexity of managing the applications increases exponentially.