Main Wiki - http://ardupilot.org/ardupilot
Editing Guide - http://ardupilot.org/ardupilot/docs/common-wiki_editing_guide.html
Gitter IM Chat -
All members of the community are welcome to join and contribute to this wiki! Any help you can offer is appreciated — from creating new articles and re-validating older articles, through to fixing broken links and spelling/grammatical errors.
We've made that very easy - all you need for access is a GitHub account Join HERE
This link provides everything you need to help the wiki grow!
See the Wiki Editing Guide