As a new user of Mango, I often wish for more complete documentation - The impression I get from the forums here is that many other users do too. In my opinion (as an end-user, nothing more) this is probably one of the biggest barriers to larger uptake of Mango. The software is great, but really requires a lot of tinkering with and playing with to understand.
I see that there is a Wiki: http://wiki.infiniteautomation.com/doku.php (which I must admit I did not know about until today!) which is a great start.
My suggestion is to encourage users to contribute by incentive, perhaps by offering module licenses for article/s written.
Another product I use (Mikrotik Routerboard), follow this model. They offer licenses for their routing software as rewards for users who write good wiki articles. As a result their wiki is chock-full of high quality illustrated how-tos, tutorials, guides, application examples and much more, making it a fantastic resource. And it was almost entirely community written!