I like the special diets idea.
Even better with hacking is that you can have a community-voted hack of the week (where you can't vote for yourself) and people upload their photos. Even better, you can offer those winners one of next week's recipes for free, in exchange for rights to their photos. So that you can uploads those photos in time for next week, and also get some valuable feedback.
Argh, even thinking about this is getting me excited.