Desk-top 3D printer - competition idea.
Fab@Home is a scheme where people build their own 3D printer ("fabber") and print ... anything, made of.... anything - silicone, glue, frosting (icing). Their dream is to send fabbers into space on autonomous probes - they find somewhere interesting to investigate, they print a robot suited to the environment. If conditions change, print a different robot. Things get busy, print another printer! (Von Neuman, can you hear me?).
Apparently one kid won a science fair by printing a map in chocolate!
They have a wiki, including a page of ideas.
Doesn't that strike you as a great project for Instructables?
How about a competition - design something to be printed by a fabber, and win your design, printed by somebody's fabber.