Well, I’ve just installed the Performancing Plugin for firefox. And I have to say, so far it kicks ass! Having a split screen interface from within firefox in which I can type my blog posts, make notes, post to any blog I want to (wordpress, blogger, movabletype etc), all the time being able to search the interenet and browse is great. Its even WYSIWYG! This could actually be a stand alone blogging tool without too much trouble.
The only thing left I can see is for my notes and settings to be stored centrally so I can blog from any browser with the plugin installed!