The Daintree website is an excellent resource for those embarking on a Zigbee project. They have whitepapers, tutorials, demos that help you understand
the basics of Zigbee networking (specifically their Zigbee primer whitepaper) and application profile object model in Zigbee.

http://daintree.net/partners/ti-chipcon.php

Their sniffer tool is a powerful ally when debugging Zigbee systems.

May the SNA be with you, always....