If you happen to be the owner of a blog, free or not, and you post often, this is a great plugin. You enter the URL of the blog, some API URL or something comes, click okay, and then you enter you username and password on the blog. You can then click the button at the bottom of FF, and publish a post to any of your blogs.
https://addons.mozilla.org/en-US/firefox/addon/1730


And something I just saw for gmail owners.
https://addons.mozilla.org/en-US/firefox/addon/1593

Enjoy!