Buzzfeed recently struck upon a winner.
They pick a popular group and write about some funny occurences amongst that group. 
It should be obvious why this is popular.
1) Group identity. It’s about a group who derive a large part of their identity from thisgroup. We like to read information about the groups we belong to. The meta-information is typically more popular than latest news.
2) Symbols. Every post is filled with symbols that have a unique meaning to that group. The posts are only funny/interesting, if you’re a member of the target group.
3) References history/shared stories. This content creates a sense of connection among the members of this group. It reinforces the community identity by referencing its own history and shared story (some might say, myth-making).
4) Networks. The bonds between these groups are strong. There is an easy medium (typically Facebook/Twitter) to share content among these groups.
The takeaway here could be that you start a discussion in your community asking what’s the most {topic} things that have ever happened? This would probably be popular.
The better takeaway is to infuse the elements above (notably symbols and references to shared history) throughout your entire community.