Points and recognition of top contributors is a good starting point.

Ted from UBM also created a The specified document was not found. a while back to promote how the community is helping its members.

Another idea, once your community gets up and running, is to have a video contest of how the community is helping.

EMC did this in their community and worked out great-

To check it out in detail here's the link within their community - https://community.emc.com/community/edn/blog/2009/07/02/youredn-videos