Microfinance institutions discovered that establishing groups to repay loans reduced the default rate. i.e. People are more likely to repay loans when they commit to going to regular group meetings, handing over the money at the meetings, and discussing relevant issues.
This works because of group commitment and peer pressure.
Group commitment is powerful. We don't want to let other people down. We'll gladly let ourselves down (or strangers down) many times over before we let other people in our groups down.
If you want to regularly go to the gym, for example, it's best to arrange for a group of friends to go at the same time. You're no longer accountable to yourself, you're accountable to a group.
Right now, you have members that have goals on their mind.
They're more likely to achieve those goals if they have others also committing to the same goals, reporting/tracking progress, and helping or competing with one another.
Initiate a discussion asking members what their goals are, then create smaller sub-groups, mailing lists, or forums for those that share similar goals.
You can make your community a place where members come to achieve their goals. That should benefit everyone.