Mozilla yesterday released Firefox 3.6.4, and on top of the usual bug fixes and security patches this new version contains an interesting feature - "out-of-process plugins" (OOPP).
What is OOPP? Well, it's a feature that means that when a plugin decides that it's had enough and crashes, it doesn't bring the whole browser down with it. Firefox pulls off this feat by running plugins such as Adobe Flash, Apple Quicktime or Microsoft Silverlight plugins in a separate process. It also means that if a plugin starts to misbehave, you can kill the plugin without having to kill the browser.
Note: Currently this feature is for Windows and Linux. OOPP for Mac is not expected until Firefox 4.
If (or more realistically, when) a plugin crashes, all you need to to is to refresh the page to restart the affected plugin.
Updates to Firefox 3.6.4 (and Firefox 3.5.10 for those sticking to 3.5.x for now) also fixed nine security vulnerabilities - six of these were rated as critical. So even more reason to upgrade.
Full release notes here.