The tarball with sources of Kamailio 3.0.0 RC1 is available at:
http://www.kamailio.org/pub/kamailio/3.0.0-rc1/src/kamailio-3.0.0-rc1_src.tar.gz
Target of release candidate is to ease the usage and testing. It is a version with a huge set of new features and enhancements, the first one using the SIP Router core framework, thefore we focus on heavy testing.
There is also now a tutorial to guide the installation of Kamailio 3.0 branch from GIT repository:
http://www.kamailio.org/dokuwiki/doku.php/install:kamailio-3.0.x-from-git
Two wiki pages were created to collect what is new in Kamailio 3.0 and how to migrate to this version:
http://www.kamailio.org/dokuwiki/doku.php/features:new-in-3.0.x
http://www.kamailio.org/dokuwiki/doku.php/install:1.5.x-to-3.0.0
Both documents still need a lot of care since many new features are missing or are not detailed, and definitely update guidelines do not cover all changes. Anyone can contribute and that is very much appreciated.
As we keep hunting and fixing issues, improve documentation, I hope to get to full release Kamailio 3.0.0 very soon. Enjoy RC1 meanwhile and report any issue you find to sr-dev at lists.sip-router.org.