Dealt with this many times, but usually, the pattern I've seen is that a majority of folks share the same challenges.

A quick poll each month of the top 3 issues or opportunities from the group- and create a conference call or webinar. Benefits are that it is results focused, and buy-in is pre-built in since they are addressing their issues (you just have to deliver). Usually there are folks successfully navigating the issues that are willing to share their successes (which can also help motivate others).