User Group - the best place to ask questions about using ZAP
Developer Group - ask questions about the ZAP internals
HUD Group - ask questions about the ZAP Heads Up Display internals
IRC - chat with core ZAP developers on the #zaproxy freenode channel (European office hours usually best)
Evangelists - people happy to give ZAP talks or training around the world
Issues - see known issues and feature requests and raise new ones
Bug Bounty Program - for reporting any vulnerabilities
Contributing Guide - lots more details on how you can get involved
Source Code - for all ZAP related projects
Crowdin (GUI) - help translate the ZAP GUI
Crowdin (Desktop User Guide) - help translate the ZAP Desktop User Guide
Student Hall of Fame - Students who have made significant contributions to ZAP
Supporters - Companies who have supported ZAP in a variety of ways
Success Stories - See how companies are using ZAP right now
Third Party Products and Services - Third Party products and services that use or integrate with ZAP
Third Party Engagement - How Third Parties can use ZAP and engage with the ZAP Core Team