Courtesy of Jon Bonilla and SIPdoc.net, latest Kamailio 3.0.x can be installed via apt package manager from repositories hosted by the project. You can find details specific for Debian Etch, Squeeze and Lenny, plus Ubuntu Lucid at:
https://www.kamailio.org/dokuwiki/doku.php/packages:debs
Being hosted and maintained by members of our development team, the repositories are updated frequently, giving instant access to latest stable snapshots. Enjoy!