I saw this over on the Stack Overflow Blog.
Sponsor fun things for each community… especially the kinds of things that are likely to get talked about. This may mean photo contests for the photography site, cooking classes for the food and cooking site, etc.
This got me thinking of what could be "fun" for our site. First I think that we should consider reviews as a valid "question" or community wiki. Some of the best RPG forums have good reviews.
Second we should encourage people to throw up things to be playtested or used. I know this has been touched in the list and collection topic.
Third have topics with more elaborate collaborative efforts like creating a setting or module.
A final suggestion is to encourage and reward people who post actual play reports.
Anyway I generally suck at coming up with "fun" community things. But I think that between us we can come up with some good ideas as I think the blog post makes an important point especially since we are not as technical as other stack exchange.