What activities, if any, are currently being done to promote MO? Have opinions changed from two years ago with this post?
I have done some independent efforts to promote MathOverflow, primarily by talking to small groups, including groups both at ICM2010 and ICM2014. In addition to some conference members (most notably Mariano Suarez-Alvarez and Charles Siegel), I was aided by StackExchange and Tim Post in particular, who helped with swag, to distribute at ICM2014.
The MathOverflow foundation was also supportive of my efforts, and is looking for additional ideas and volunteers. You can contact them through moderation email firstname.lastname@example.org. You can also contact me using my email address provided in MathOverflow @ ICM2014 : We Want You!, or https://mathoverflow.net/users/3206 or https://mathoverflow.net/users/3402 .
While I and others are considering several possibilities, it will come down to getting the right word out, and providing the right service. MathOverflow has grown reasonably well because of the service it offers and the word-of-mouth provided by its community. In my opinion, to ensure continued growth, it will need to consider offering new services to attract more members, while maintaining the quality content that comes from a knowledgeable user base and ceaseless community moderation.
I look forward to hearing your ideas.
Gerhard "Not Community Relations Manager, Yet" Paseman, 2015.08.31