I helped with something last summer: an attempt at creating a wikibook for D.  At that time, my D skills were very bad, so I had to concentrate on learning D first before contributing to more lessons.

One thing that has always bothered me is, there aren't many good *free*
ebooks for learning D.
Well, I'll try to continue what I had started less than a year ago.  I'll
probably make many mistakes while writing, so can you guys check on my
progress once in a while?

http://en.wikibooks.org/wiki/D_(The_Programming_Language)/d2/Lesson_1/Phobos

What do you think?
Thanks.