Sailor Moon Land
So, I joined this community about a month ago, and it's LOTS of fun! It's a battle style community (you're sorted into one of 3 teams) and every week there are new challenges: graphics, writing, puzzles, etc. The points you earn in the activities are combined with your team's points to get the overall score.
Anyway, it's a lot of fun, and you don't even need to know a lot about Sailor Moon to do it (or be a good writer or graphics maker-- I suck at graphics). You can participate as much or as little as you want (if you don't want to participate in 4 challenges a month, you can be a social member).
Anyway, check it out and come play. http://sailormoonland.livejournal.com/profile