Debian Linux is released as three versions, stable, testing, unstable. every release has a code-name but unstable is always called as sid, in which has most recently packaged utilities with cutting edge features.
oh... too long, I don't have to explain everything about Debian here.
For sid, I can have only two lines in /etc/apt/source.list file.
deb http://ftp.kr.debian.org/debian/ sid main contrib non-free
deb-src http://ftp.kr.debian.org/debian/ sid main contrib non-free
The source contains the most recent updates including security updates. It's cool.
