If you would like to get involved in the development of IntelliJ IDEA, use the following info on what you can do.
Getting latest development builds
IntelliJ IDEA Architectural Overview
IntelliJ IDEA Action System
IntelliJ IDEA Plugin Structure
Plugin Development FAQ
Build Number Ranges
Building Plugins with IntelliJ IDEA 7.0 and 8.0
Developing VCS Integration Plugins for IntelliJ IDEA
Diana Plugin Migration Guide
Developing Custom Language Plugins for IntelliJ IDEA
API changes in IntelliJ IDEA 9 (Maia)
IntelliJ IDEA Virtual File System
DOM & JAM (rapid support for XML- and annotations based frameworks)
Localization Guide for IntelliJ IDEA
Participating in discussions
There are a few newsgroups at our news server (news://news.jetbrains.com).
- jetbrains.intellij.community General user community discussions
- jetbrains.intellij.eap Main group for the Early Access Program (EAP)
- jetbrains.intellij.eap.announcements Announcements of new EAP builds
- jetbrains.intellij.eap.j2ee Discussions related to the J2EE support
- jetbrains.intellij.openapi Discussions related to the APIs required for plugin development
- jetbrains.intellij.plugins Discussions related to various plugins for IDEA
Most of the groups are replicated to the web-based forums.