As UC platform is gaining momentum among developers, here are some resources about the blogs/forums related to UC platform in general. They also contain lot of information in particular about writing UCMA 2.0 applications.
Unified Communications Development blog : http://blogs.claritycon.com/blogs/michael_greenlee/default.aspx
OCS R2 Server Side Application Development (SDK)s – UC forum to post questions : https://ucforums.microsoft.com/forums/361.aspx
A website dedicated to UC developers http://gotuc.net/default.aspx