Firefox 3.6.4 has finally arrived, and as expected it brings added stability by making Adobe Flash, Apple Quicktime or Microsoft Silverlight plugins run on their own process, so if something goes wrong with them, your whole session will still survive and you will be given an option to reload the plugin.
While Silverlight, Flash, and QuickTime are supported out of the box as they were subject to intense quality control, you can actually run any plugin on its own process. You just need to know the name of the plugin library (which you get from about:plugins),
For example to have the Adobe Reader plugin running on its own process, create a boolean preference in about:config, name it dom.ipc.plugins.enabled.nppdf32.dll, set it to true, and restart. For Java, the preference must be named dom.ipc.plugins.enabled.npjp2.dll, and so on.
Conversely, you can disable OOPP for enabled by default plugins by creating and setting their respective preference to false.
This update also includes fixes to four critical and a few other less severe vulnerabilities, so you are strongly encouraged to update right away. Just click on Check for Updates… in the Help menu.
You can get more details in the release notes.