In case you muck up your /etc/apt/sources.list and want to set it back to the defaults, just copy and paste this in:

deb http://ftp.debian.org/debian/ etch main
deb-src http://ftp.debian.org/debian/ etch main

deb http://security.debian.org/ etch/updates main contrib
deb-src http://security.debian.org/ etch/updates main contrib