List configured APT data sources for binary packages using apt-cache utility.
Notice that this solution will not list repositories for source packages.
First approach
The simplest approach is to use apt-cache utility to print package repositories.
$ apt-cache policy | awk '/http/ { printf "%s %s\n",$2,$3 }' | sort | uniq
http://ftp.us.debian.org/debian/ wheezy-backports/contrib http://ftp.us.debian.org/debian/ wheezy-backports/main http://ftp.us.debian.org/debian/ wheezy-backports/non-free http://ftp.us.debian.org/debian/ wheezy/contrib http://ftp.us.debian.org/debian/ wheezy/main http://ftp.us.debian.org/debian/ wheezy/non-free http://security.debian.org/ wheezy/updates/contrib http://security.debian.org/ wheezy/updates/main http://security.debian.org/ wheezy/updates/non-free
Second approach
Modify it a bit to pretty-print the parsed data.
$ printf "%-60s %s\n" "URI" "Suite and section"; apt-cache policy | awk '/http/ { printf "%-60s %s\n",$2,$3 }' | sort | uniq | sed -e "s|\(.*\)\/|\1 |"
URI Suite and section http://ftp.us.debian.org/debian/ wheezy-backports contrib http://ftp.us.debian.org/debian/ wheezy-backports main http://ftp.us.debian.org/debian/ wheezy-backports non-free http://ftp.us.debian.org/debian/ wheezy contrib http://ftp.us.debian.org/debian/ wheezy main http://ftp.us.debian.org/debian/ wheezy non-free http://security.debian.org/ wheezy/updates contrib http://security.debian.org/ wheezy/updates main http://security.debian.org/ wheezy/updates non-free
You can quickly extend it to print out the priorities of each source.
