The reference wiki is located here. It's a resource at Anthologica targeted at helping people develop content—and get around the site. So far we have a few projects on the go; Nessari is working on cleaning up the Natlangs hierarchy, Nort (with help?) has been developing a vowel systems reference work from old Zeeb material, and I've put up a little bit of stuff on writing systems that I plan on extending further. It's also the place where the Anthologica Documentation can be found.
The reference wiki is open to everyone, though for neatness's sake you must request access to it first. Drop me a message if you want in. (Or just ask here!)
To start things off, I thought I'd ask what sort of documentation/tutorials people think the site needs. What's hard to do right now? I recently added a Footer Quotes page so you can see all of the various weird things that pop up on page refreshes without hammering the server O(n²) times, as well as a general Site Statistics page that lists overall counts.