To chat with players and browse live games, download the game and join the lobby.

Without the lobby, you can join the gitter discussion channel

Open Source on Github

TripleA is an open source project hosted on Github. Material on getting started as a map maker can be found on the Github Map Project page

TripleA War Club

Community website with ladder, tournaments, and forums for finding matches and discussing game strategy.

AxisAndAllies.org

AxisAndAllies.org is a great resource for TripleA and Axis and Allies players. It has vast forums, alternate rules, and website.