Mozilla has a released for download and testing purposes a Beta version of the upcoming Firefox 3.6.4 (Lorentz). Included in this release is the new Out Of Process Plugins (OOPP) which allows Plugins (currently Adobe Flash, Apple QuickTime and Microsoft Silverlight) to run in a separate process from the main Firefox process. With OOPP, if a plugin should malfunction and crash, only the tab(s) containing the plugin will crash instead of taking the whole browser down. Google Chrome is a browser which uses a type of OOPP technology.
The public release for Firefox 3.6.4 is currently scheduled for May 4th, 2010.
Source:: Mozilla Developers News