In case you haven't noticed, the XUL tutorial is now available as part of the Mozilla Developer Documentation site. An advantage of this is that errors can be corrected quickly and by anyone who spots them. The user notes created by users haven't been transfered though. I'm not sure if that's a good thing or not.
The user notes include a number of useful tips that people have written relating to a particular page. Currently the user notes aren't posted until I actually read them. This is a good thing since half of the notes are either questions (which I usually just ignore), or are misleading or incorrect. On one hand, I don't want to discourage someone by not accepting a comment they've made, but on the other hand, I feel that if a comment is misleading or uses, for example, some code that is a bad way of doing something, I don't want to post it, since the point of the user notes is to improve the documentation.
Anyway, I think there are plans on posting some other XULPlanet stuff, and I also plan on posting the template guide I've been writing on here. The Aaron countdown timer seems to have disappeared recently perhaps indicating his return a few days early so maybe the App tutorial or Prefbar will get updated also.
In other news, I've been hacking a bit at templates using XML data. Here's the first ever image of a XUL template fed with only XML input. It doesn't look very exciting but that's because the excitment is in disguise. Vlad's just reviewed the main part of the code for this, so we could very well see this stuff early in the 1.9 timeframe.