Hello,
development guide for Kamailio has been updated for v3.2.0 - it goes through internal components, presenting the APIs for pkg/shm memory, locking/synchronization, config file interpreter, database connectors, a.s.o., as well as guiding how to write a new module. There is a section trying to collect hints about upgrading a module developed for old versions 1.x to newer architecture and APIs in versions 3.x.
The tutorial is available online at: * http://asipto.com/u/kdg
A mirror is hosted at: * http://www.kamailio.org/docs/kamailio-devel-guide/
This is the first release for v3.2, it may get adjustments in the near future. Among the plans to add new chapters: how to write docbook documentation; TM module API, Presence module API ...
Cheers, Daniel