I would say wikisource.org since DjVu are mainly used on WS (there are a
few DjVuS outside WS but not many many, perhaps inside institutions). If
you are interested by the DjVu, you can browse
<http://www.djvu.org/resources/>, but DjVu specifications are quite
unreadable. Briefly, there are many layers, whose text is one layer, there
are also annotation layers, many layers for the image, etc. DjVu is really
powerful but really badly documented. So if you write some documentation
 from scratch, it will be quite the first documentation readable (I thought
some time ago write a wikibook about DjVuS but didn't done it).

Sébastien