Hello,
I setup an apt repository for kamailio 3.0.x, holding now debs for lenny i386 and ubuntu 9.10 i386. Add to your source.list:
- for debian: deb http://kamailio.org/pub/apt/debian lenny main contrib non-free
- for ubuntu deb http://kamailio.org/pub/apt/ubuntu karmic main contrib non-free
then apt-get update and apt-get install kamailio.
Cheers, Daniel