As you know, I'd like to experiment with prototyping some new interface concepts for package managers.
I put together a prototype backend and hacked a cmd-based shell interface for
it.
You should be able to fetch it with:
bzr branch http://people.debian.org/~enrico/2007-01/popcon/
The files involved are pm.py, pmnew and a very little bit of anapop.py.
You run it with ./pmnew (it needs python-apt and python-debian installed).
The commands are:
- search Set the search string for tags
 - tags Show the list of available tags
 - desired Set a tag as desired: only packages having that tag will be shown
 - undesired Set a tag as undesired: packages having that tag will not be shown
 - nevermind Set a tag as neither desired nor undesired
 - filter Limit results to a specific kind of packages (any, devel, games, gui...)
 - packages Show the (filtered) list of available packages
 - info Show details about a package
 - install Install a package
 - quit Quit the program
 
This can be an example session to try:
tags
search toy
tags
packages
tags
desired 1
packages
info 3
If you:
- have 
popularity-contestinstalled and running - are online
 - have a writable directory called 
~/.debtags 
then the list of available packages will be sorted using my recent web interface prototype for popcon-based suggestions.
Matt Good and Thomas Viehmann volunteered to have a try at a GUI.
This can only be fun.