Wiki hilsz.com: Asterisk

http://www.asterisk.org
http://www.voip-info.org/wiki/index.php?page=Asterisk

http://www.spokentech.org/aik.html

http://en.wikipedia.org/wiki/Asterisk_(PBX)
http://www.ohloh.net/p/asterisk

http://ostatic.com/blog/asterisk-11-comes-with-long-term-support-can-replace-expensive-pbx-systems#blog
http://cdn.oreilly.com/books/9780596510480.pdf