Use the issues queue here to ask questions and offer help on using Mapnik.
The Mapnik project has a mailing list (http://mapnik.org/contact/) but why not try using github instead?
Maybe if this works well we can retire the mailing list at some point in the future?
Bug reports should be filed at https://github.com/mapnik/mapnik/issues. If you are not sure if your problem is a bug or a problem in Mapnik usage feel free to ask the question here