Some Blender-related websites host their own contests. Blender Guru presents a themed contest monthly. And on occasion, Blender Cookie (CG Cookie) will present an exercise and a follow-up review, like their Bot Bunny Exercise.
A group of participants may want to collaborate on an entry, or an individual may seek assistance.
... or we could just conduct our own parallel contest amongst our own more familiar group at our own aggregate skill base.