The source for the manual is still up, and is quite readable despite the few style annotations:

http://code.google.com/p/chibi-scheme/source/browse/doc/chib...

Note: I don't have access to the original manual link either, so I can't confirm that it's exactly the same document. It describes the language in details.

Oh hey, it's in scribble! Neat, I thought that that was an only a Racket thing...

Should be back up now - grab it while it lasts.