I'd like a photography one...
Maybe we could do something similar to a photo forum I was on a few years ago. They had an informal Daily Challenge (we could change it to a weekly challenge). The first person (or we could take a poll on subject/theme and someone volunteer to judge the first week) suggests the theme, then judges the entries at the end of that week. The 'winner' of that week suggests the next subject/theme for the following week, judges the entries and picks the next 'winner', who chooses the next theme, and so on and so forth.
There were usually six to eight 'places' awarded, with the judge giving a brief critique for each place. Some added 'Honorable Mentions', as well, if there were enough photos entered.
Something like this would take the onus off one person having to come up with 52 things to do for the rest of us... Theme/subjects ranged from basic photography techniques (low-light, perspective, panning shots, etc) to whatever the judge wanted (stacks of things, contrasting colors, unusual perspectives, old things, food, etc.) The only requirement was that the photos had to be taken during the 'contest' week, no old photos allowed, and one entry per person. (Some people did post their other photos but made sure to mark them as not part of the contest).