General game information
More information on ModDB.
The Design Document - This is the main over-view design document for the game. It should give you a good insight to the game workings and big-picture.
0 A.D. Gameplay Manual - details on how to run the game.
0 A.D. Modding Guide - overview of modifying the game. What tools you need, where the files are located, etc.
Installing the East Asian Locales mod - see how you can add support for locales that require a more elaborate font.
Forums and Community
Development & Technical Discussion for developer discussions. (See also new forum posts since your last visit, if you check frequently. You can also filter the forums to only include development forums if you want to just get the relevant posts without having to skim over off-topic posts and similar.)
#0ad-dev on QuakeNet IRC for developer discussions.
Human Template (RAR'd PSD)