Due to the activity on this meta question and this question it is evident that the users want a more active site, and to boost the reputation of available users, both of which I think are excellent ideas.
Here are two meta questions from a graduated site, movies.se, one is a challenge for solving old unanswered questions (scifi.se also does this), and another is for a topical challenge, where the users themselves are challenged to generate content on a specific topic.
I think both of these ideas have a lot of merit, so I would like to propose making the first week of every month one where the current users go through the unanswered questions, and either flag/vote to close if they are off topic, or answer/encourage experts they know to come and weigh in. The second we can do on an interim basis, with topics to be suggested.
I'd like to see how the community feels about implementing these here, so please leave answers with your perceptions and suggestions.