debian packages - what version is available and from which repo?

'apt-cache' madison is the answer.

Example:

giavac@myhost$ apt-cache madison vim
       vim | 2:7.3.547-7 | http://ftp.uk.debian.org/debian/ wheezy/main amd64 Packages

From apt-cache man page:

 madison pkg...
           apt-cache's madison command attempts to mimic the output format and a subset of the functionality of the Debian archive
           management tool, madison. It displays available versions of a package in a tabular format. Unlike the original madison, it can
           only display information for the architecture for which APT has retrieved package lists (APT::Architecture).