The Mozilla Foundation has published a check for web browser plug-ins. Just by visiting the web site you can immediately see if your plug-ins are up-to-date (green), outdated but without known vulnerabilities (yellow) or if they are known to have security holes and are outdated (red).
The check is supposed to work for Java, Adobe Reader, Flash, Shockwave, QuickTime, Windows Media Player and DivX. Supported operating systems are Windows, Mac OS X and Linux. If a plug-in is outdated, you can click on the button next to it to be sent to the manufacturer’s homepage and fetch the update.
Firefox 3 did warn of an invalid certificate. As the check isn’t final yet, this may be tolerable – but if the service gets official, Mozilla should definatly fix the certificate.
Update: Now the Mozilla Foundation has made this service official, you can reach it here. There is no warning of invalid certificates involved anymore!