During the PyLadies lunch here at PyCon, I heard 5 people stand up and say that they would not have given a talk if an individual (in many cases Jessica McKellar) hadn't pestered them repeatedly to give a talk. I saw later that someone else had heard this from 10+ people at the lunch.
Increasing speaker diversity is both about sending emails "to the right mailing lists" but it is also largely dependent on individuals reaching out to new (and veteran) speakers to get them to submit talks.
So - a lot of this work has to happen on multiple fronts at the same time - the CFPs need to go out to lots of lists, and individuals need to reach out to lots of individuals.
The only way I have seen this be consistently successful is if many people on the conference committee are all making individual requests to speakers, and the people making the requests are trusted by the talk submitters. It's a systemic issue involving visibility, trust, mentorship in general, talk submission mentoring, and mentorship of talk creation, rather than something that can be solved with adding additional places for CFPs to be sent. Several women commented that they might have cancelled their talk after arriving in Montreal if they had not had support from PyLadies and other community members hours before they gave their talks.
More diverse members of the conference committee, that have time to do outreach, that can reach into new communities that trust the person who is asking, is a critical step in the process of increasing diversity.
@bcostlow: I've been thinking about this but I don't have much more to offer other than recruiting people who are part of more diverse communities to your organizer group. There are a few people whose work is increasing diversity in organizations, and I think it is often worth paying them for a few hours of consulting to look at the specific opportunities and needs of an organization like PyOhio.
The good and bad news is that change like this takes time. PyCon took 4 years and the work of a very dedicated team, whose most important leaders are so committed to changing the diversity of Python language development itself, that they make divisive public statements like "I will only take Q&A from women in my keynote" (Guido van Rossum).
So, my other piece of advice is to make the change process take less time, get a commitment from the leaders of the organization to make statements publicly that address the change in culture that comes with having women be involved. You may already be on this path, I don't know.
A common issue in organizations that are divided politically over the value of diversity efforts is that part of the organization will state that they "want more diversity" but then another part of the organization will undermine those efforts quietly but effectively in the background. I'm not saying that's happening at PyOhio -- I'm just pointing out that there are lots of factors, a lot of social forces at work, and having someone whose focus is on diversity change in organizations come and offer advice can be a way forward. And I'm not that person. :)