You can't get things to work any more organic than this! Every wednesday a new topic is announced at @togchat. By using the hastag #togchat anyone can join in on the discussion.Check @togchat for the newest topic!
A Twittersearch on that hashtag will bring al lot of photorelated tweets to the surface anyway. Nice! with all these interesting discussions one just might lose track of time and forget to actually shoot some pictures ;)
You'll find communities and competitions here. Both are motiviting and inspiring. In some way participants form communities too ;)