Last year, in 3rd grade, my youngest did a probability poster dealing with M&Ms (probability of pulling a certain color - there is information online about the distribution of colors). She handed out small M&M packets to each kid. Of course, it might not work with the small packets, but we also bought a very large bag of M&Ms to see if it matched the information online.
Middle kid did a poster for her confirmation project on Fibonacci sequences in nature. I don't know that the minister liked it, but a church member who was a former math teacher thought it was great.
