Warning! All the projects here are very outdated, and won't work with modern mozilla products.
I've created a javascript class for accessing the Google APIs, you can download it from this page. I've only used the spellchecking functionality so far, so the rest is untested. You may need to enable some privileges in Mozilla to get it to work.
This script was spun off of Livelizard, which is a Livejournal client. More info at both of those URLs.
I've started work on an <editor> tutorial here. I don't yet have time to write the view source tutorial, but so far it has enough information to get you up and running using <editor>.
I saw bug 32594 and I decided to make a package out of it, so go get the History Sidebar Panel.
The Links Sidebar Panel collects URLs from the page and displays them in the sidebar for easy clicking.
The Link Toolbar is a fix for bug 2800, and allows browsing of <link> elements for a page.
Composite builds upon Mozilla's <editor> widget to enable WYSIWYG HTML editing for textareas. ComposIte was co-developed with Andy Edmonds and borrows code from Livelizard.
Livelizard is a client for the Livejournal journaling system written for Mozilla. It currently supports all posting features except friend groups. Livelizard is written in XUL and JavaScript.