I've served as PyCon's volunteer publicity chair the past two years. This year, at my request, the attendee survey had the question, "How did you hear about PyCon?"
Thanks to everybody who took the survey and answered that annoying question. Of course, most answers were along the lines of, "Duh, I've always known about PyCon!"
Basically, the answers helped to confirm that community buzz is what brings most people. (My favorite answer: "Birds.") Problem: not everybody is plugged into the buzz. I know lots of programmers who never read blogs or attend groups, and there are lots more that I don't know because they don't do blogs or groups, or otherwise plug themselves into the community.
What I most need is for everybody who didn't hear about PyCon to answer this question: "Why didn't you hear about PyCon? Where would you have seen a PyCon announcement?" The logistics of doing that survey are tricky, however.
How do you think word spreads among geeks, in this day and age?