It’s not free publicity, but I think that organizing a multi-genre convention for only Creative Commons-licensed and other freely-licensed works (literature, music, performance art, etc.) would be a good means by which users of Creative Commons and free media licenses from all genres and niches can meet face-to-face, promote their works, and collaborate. It could be massive, and it could lead to the furtherance of a fandom or devoted following for such works.

Of course, there’s the iCommons iSummit, but I’m not sure if it’s going for the sort of elevation that is most associated with fan conventions.