Write roundup posts!
The posts I've made that I think yielded the most value for the amount of work I put in were essentially lists of other people's work.
EA Syllabi and teaching materials
Giving now vs. later: a summary
There are other formats that may make sense, like tags for material on this forum, or wikis. But the general principle is that you can do something really useful by making it easy for people to find existing material on a topic.