Earlier this year the British Broadcast Company launched Get Writing, an educational site on creative writing. The site features space for aspiring writers to save their works, learning modules about writing, and forums for writing discussion.
They even have my favorite ruse for focusing user activity: contests!! But they also reminded me of something else quite useful that I should have remembered from teaching: easily generated challenges which students can readily evaluate themselves against.
I wonder if Philip Greenspun baked any similar ideas into photo.net