Collapsable nested quotes. This is a great little script written by pankeki, used here with permission. You can thank him for it, or find out how to use it in other browsers like Firefox if you're into that, over on his forum thread.
Keeps basic track of your reading progress on forum threads. Links from the "Recent" section of the dashboard will take you straight to your last read page. I know, another feature that appears ripped off - though I actually wrote the implementation for this prior to this next one's release. If you want even more features related to this, you can check out thenn42's new extension.