Probably you'll wonder what's that.
Ok, WriteArea is a Firefox extension that embeds FCKeditor 2.5 inside the browser, so you can launch FCKeditor on any plain textarea and easily edit HTML without having to deal with all the source code.
For the moment it is "sandboxed", that means that it won't be available when you go just searching for an extension, instead it's available only in the Sandbox, where the new extensions are placed until enough people have reviewed them, in fact, you need to register and login to http://addons.mozilla.org in order to view it.
As I've said it needs enough people to verify that it works correctly before is available for everybody, so I would please ask you to test it and if possible write a favorable review :-)
Disclaimers and acknowledgements:
Some ideas grabbed from Xinha Here!
Icon created by http://deleket.deviantart.com
And of course, FCKeditor is © www.fckeditor.net
Of course this post has been written using this extension ;-)