There seems to be some interest in the idea of an annual community event, so I'm going to propose some suggestions as answers for voting.
The basic idea is a photography contest around images shot on that day and follows the standard rules of the POTW contest. The big difference in this one is that the winner gets the banner for an entire month (could be a calendar month or 4 weeks) and entered into a dedicated hall of fame.
Image must be shot on that day.
Voting lasts for 2 weeks.
Voting and image rules match the standard Picture of the Week practice.
Winner is on the site banner for 1 month.
Feel free to refine this idea or let me know if I'm nuts. Please also suggest other days for this if you have a suggestion that you think might be more interesting or suggest an entirely different event for the community to participate in. It could be a one-time only or a recurring event, either is fine, just something to spark the fire a little here.