While browsing through the Firefox extension site I noticed cuneAform – which appears to be a browser-based editor that is embeddable in a web page. These are JavaScript components that you can add to a web page and that give users a word processor-like experience with a toolbar offering text manipulation functions (bold, italic, etc.) and more HTML-specific functions (styles, tables, image upload).
In the past, these editors sorta sucked because they were browser specific (I used soEditor which is IE specific and checked out BitFlux which was pretty hostile and did not work with IE). The best such editor I actually used is the Hardcore Internet editor which works really well and the company that produces it offers spectacular support for it. [Spectacular = bug resolution in less than 12 hours]
cuneAform is interesting in that it is both free and that it works with both browsers and is free. I did not check it with Safari or with Opera as this functionality normally is used in a client’s back end of a CMS application and hence the client can enforce the browser that is in use. In the past, that was an excuse to require IE to be used but allowing Firefox is just so better.