The apt version we use in Ubuntu has the nice feature to support translated package descriptions. This means that “apt-cache show apt” (or synaptic) will display a german translation if the user has a default german locale. Translating those this is a big task, there are plenty of packages so there are plenty of descriptions.
To make working with the translations of these descriptions in launchpad easier there is a now new website that sorts the package descriptions and presents them in a nice and easy way. It was written by István Nyitrai and is available at http://people.ubuntu.com/~mvo/nightmonkey . I think its very cool, have a look and give feedback to the author.
The debian project uses a system called DDTSS: http://ddtp.debian.net/ddtss/index.cgi/xx that looks a bit different (and does of course not contain ubuntu specific package like the ones in restricted). We are currently working with Debian on a way so that we can push the translations.launchpad.net translations back to Debian. We already sync regularly from Debian, having a working system in both direction is going to rock🙂