Yesterday, I built and packaged win32 binaries for Mapnik. All libraries including dependencies are built with VC++ Express on Vista.
There is no installer (yet) so you have to setup %PATH% etc yourself. In 'bin' directory (e.g c:\\\\mapnik\\\\bin ) there is a small demo application 'rundemo.exe' which produces two map images from demo data. You can run it like this:
Everyone (with Windows box) is encouraged to give it a try and report any problems, gotchas ... If everything is OK then win32 binaries will be available as a part of Mapnik release, starting from 0.4.1.