Scribe seems to be a rather cool new Firefox extension. It allows you to load and save text that you are typing in a text box.

I often compose meeting notes in a emacs and then copy the text over to MovableType, where I then do some additional touchup. A plugin like this might help me keep the two (MT entry, text file) better in sync. It will also help in cases where the wireless suddenly drops out mid-way through composing a post.