A list of frequently asked questions (and their answers) is available here: Frequently Asked Questions
Training options are now available: training
Checkout our Discourse at https://forum.suricata.io/
Tracking bugs, feature request and support requests is done on our redmine.openinfosecfoundation.org
We have an IRC channel on freenode.net, join #suricata.
Most of our development revolves around our redmine site: redmine.openinfosecfoundation.org
Our mailing lists are being phased out in favor of the forum: https://forum.suricata.io/
The old lists and their archives are still available at lists.openinfosecfoundation.org/mailman/listinfo