Which installed pkg belongs to which release?

["Thomas Gebhardt" <gebhardt@HRZ.Uni-Marburg.DE>]

Hi,

starting from a "clean" installation, after applying security patches,
and installing "unofficial" .debs, backports and self-compiled packages,
the set of installed packages can get rather messy.

Is there an easy and recommended way to scan the list of installed
packages against an apt-get source.list and get a comprehensive
list of all installed packages, each assigned to (at least) an
apt-get source or marked as "unavailable"?

Thanks for any hint!

Cheers, Thomas