ANTLR Community Support
ANTLR is supported by Terence Parr, Sam Harwell, and target language folks (see top of the code generation targets documentation) as well as the multitude of helpful users of ANTLR.
ANTLR Questions
Stackoverflow.com is our question and answer mechanism:
http://stackoverflow.com/questions/tagged/antlr
http://stackoverflow.com/questions/tagged/antlr4
ANTLR Discussions
Please do not start discussions at stackoverflow. They have asked us to steer discussions (i.e., non-questions/answers) away from Stackoverflow; we have a discussion forum at Google specifically for that:
https://groups.google.com/forum/#!forum/antlr-discussion
We can discuss ANTLR project features, direction, and generally argue about whatever we want at the google discussion forum.
ANTLR v3 INTEREST ARCHIVES
The archives from the previous mailing list dealing with v3 may still be of use to you:
http://www.antlr.org/pipermail/antlr-interest/
Official ANTLR IRC
Channel is called ##antlr and lives at irc.freenode.org. (Terence does not listen to this channel)