Ace3 - AddOn development framework
Ace3 is a comprehensive framework for WoW AddOn development to streamline many of the common tasks in developing addons. This includes lifecycles, saved variables, configuration, event handling, network communications, and more.
Documentation
A basic introduction to usage can be found here:
https://www.wowace.com/projects/ace3/pages/getting-started
Documentation can be found here:
https://www.wowace.com/addons/ace3/pages/
For historic purposes, the "old" documentation is still around on the old wiki, some articles may not be converted yet, and only exist on the old wiki:
http://old.wowace.com/wiki/Ace3
Resources
A development repository is available on GitHub:
https://github.com/WoWUIDev/Ace3
Please note that the CurseForge/WoWAce SVN repository remains the primary authority, and what should be used in .pkgmeta to reference Ace3.