Interesting: Really Simple Discoverability via XML, plus Mozile, a browser-based in-line HTML editor. Currently rolling it into my site, although it looks like Mozile only submits the text you're editing (or the whole page), so need a way to identify which page it's for. A hidden comment would do, I guess, but seems like there should be a better way. (May implement a RewriteRule to spit back a correct RSD file that incorporates the info instead, but this still seems a long way round...)
Keep thinking about releasing the code behind exmosis.net at some point, but right now it's too messy.