Esta es la lista que utilizo en mi sources.list para mi debian 5.0.7, quizás a alguien le sirvan:
deb http://ftp.us.debian.org/debian/ squeeze main contrib non-free
deb-src http://ftp.us.debian.org/debian/ squeeze main contrib non-free
#SECURITY
deb http://security.debian.org/ squeeze/updates main contrib non-free
deb-src http://security.debian.org/ squeeze/updates main contrib non-free
#UPDATE
deb http://ftp.us.debian.org/debian/ squeeze-proposed-updates main contrib non-free
deb-src http://ftp.us.debian.org/debian/ squeeze-proposed-updates main contrib non-free
#MULTIMEDIA
deb http://www.debian-multimedia.org sid main non-free