The documentation on this site is generally split across modules, so please check the section Sub-Modules in the navigation bar on the left of this page. If you need help with the client APIs, please check the comprehensive Javadoc. This is updated for every release, so it may be worth to recheck if have you been missing something in the past.
Please also check the Frequently Asked Questions.
For any bug report, improvement request, feature request, task request, help request etc. please subscribe to the User Mailing List and post it there. If you have an account on java.net, your subscription will get immediately accepted, otherwise you'll have to wait until it gets manually accepted. The response time for approving subscription requests and answering posts is usually less than a day - this goes without warranties!
Once your question or issue has been regarded as a bug report, improvement request, feature request or task request it gets tracked in JIRA. You can then use JIRA to monitor and discuss its progress, vote for it, add file attachments, download hotfixes etc. JIRA is also used to schedule new TrueZIP versions and prepare their Release Notes.
Finally, if you want to stay up to date please check The TrueZIP Blog for the latest news and announcements.