The first officially hosted draft has landed! It's still in very rough shape, so I wouldn't post this around to other websites too much. I would love feedback, and patches welcome!
The raw source is at https://github.com/rust-lang/rust/tree/master/src/doc/tarpl
The link is
it was renamed to the Rustonomicon
Why no redirect?
Because it was only up for a day or two at that link, and everything in nightly is subject to change anyway.
it might be worth it, because while I was looking for it last time someone got confused, google kept pointing at old places. I think I only realised where it was because of remembering someone questioning the choice of url placement (the /nomicon/ bit).