Scribe: a Firefox extension that allows you to save form fields, such as a blog entry post, as a local file. As someone who has lost at least a dozen blog entries due to application crashes, careless browsing, or accidental closing, this is a valuable extension.
Well, except that OmniWeb (my primary home browsing environment) has had this since version 5 came out. Actually, it’s much more robust than this since it saves everything when it crashes: from your form field text to your open tabs to each tab’s history and contemporaneous content (a lifesaver in the case of Bloglines when you’re in the middle of reading new entries in a folder full of feeds).
[UPDATE: As if tempting the Fates, my battery went dead today in my iBook. OmniWeb did a valiant job at restoring what it could of a brilliant entry but it had only stored the first few sentences of the several paragraphs I had written. Moral of the story: nothing can protect against sudden power loss (except maybe a APS.]