At our school we ran a maths unit on making 'nets' for chocolate boxes which the kids made in SU and then folded up the nets, glued them up, filled them up with chocolate, sold them and all the profits went to a charity. I recorded an SU tutorial on how to fold up the nets on screen using a programme called Camtasia which records your voice and the screen. So they could see whether or not their nets were going to work before they printed them out on card.
It was good fun and the kids loved it!!
S.