I am always on the lookout for interesting blog editors, and stumbled upon ScribeFire while working on a project on Chrome extensions. This one is already quite popular in its Firefox avatar, and a Safari version exists as well.
ScribeFire proved pretty simple to set up: just enter your blog’s URL and it fetches most of the technical details itself. You can add brand new posts or even work on your existing posts. One done, they can be published directly or scheduled for publication at a specific time. They can be saved as drafts or private posts as well.
ScribeFire supports categories, tags and custom fields. You can add a custom permalink as well. The only niggle is the inability to upload images from your hard disk. One hopes the developers are working to iron this out since it is a significant drawback.