Zabbix community
When you have finished the recipes in this book, you should have a good understanding of how Zabbix works, but you will probably also have many more questions on how to monitor certain things in your environment.
I encourage you to join the Zabbix community. Zabbix provides a page where all information is gathered from the community, http://www.zabbix.com/community.php.
A lot of information can be found on the Zabbix forums where people have posted questions and received answers for their problems, http://www.zabbix.com/forum.
If you would like to help Zabbix improve or write some hacks of your own then you could download the source code, http://sourceforge.net/projects/zabbix/ or http://www.zabbix.com/developers.php.
If you need some quick support, your best bet is probably the IRC #zabbix
channel on Freenode, where lots of people check in every day, including most of the Zabbix developers: http://webchat.freenode.net/?channels=#zabbix.
Most importantly, don't forget to check out the website www.zabbix.org where people from the community contribute all their knowledge. If you have made some templates or if you have created some interesting hacks such as Action simulator project, that tells you why you were not notified by Zabbix, then this is the page for you to share your knowledge with the rest of the community. After all, that's what open source is all about!
If you live in Belgium, then you could join our Zabbix Meetup group where people talk about their Zabbix setup or other interesting things they have done with Zabbix. Feel free to join to learn more or to host a meeting to show us your Zabbix project: http://www.meetup.com/Belgian-Zabbix-User-Group/.