The Society of Killustrators. A group founded to "hone a craft, further a trade, and stay in contact," the SOK regularly posts imaginary illustration assignments.
Started as an invite-only group, they recently opened up the assignments to anyone who wants to play along — similar to Illustration Friday, though they do still send out invites. I was honored to receive one to participate in their last assignment: Beer Macaroni and Cheese packaging. You can read more about the assignment here (including the real recipe) and see the results here.
The newest assignment is for an editorial illustration to accompany an article about thieves caught stealing $65,000 worth of chicken wings. Can't wait to see what happens with this one!