The OSM annual event is in Girona, Spain this year and it will surely be a great time to catch up with members of the Mapnik community.
I will be attending as I'm helping present on the work that H.O.T. has been doing in Haiti. H.O.T. has a presentation lead by Nicolas Chavent on Sunday called "Grounding the OSM Project: The Humanitarian OSM Team in Haiti".
At least two talks are focused specifically on cool Mapnik rendering topics:
And there is also a BOF session on Mapnik (in addition to OpenAerialMap) tentatively on friday morning, which will be a great chance to push forward ideas on the future features of Mapnik discussion from WhereCamp SF