From the Haters Gonna Mitigate the Hate dept.:
Mozilla Firefox 3.6.4 went to general release today. The big new feature in this release is out-of-process plugins (OOPP). This means things like Flash, Java, QuickTime, etc., all run in separate processes, so when Flash decides to crash, it won't take your browser out with it. If Flash starts consuming all the CPU it can find, you can kill it without nuking your browser session. I've been using this feature since it was in the 'nightly build' stage, and it was still more stable than 3.6.3, just because Flash was isolated."

slashdot.org