Legos....a favorite toy for kids, so that their parents can "help" out and play as well. Now, people are showing that some serious mathematics can be accomplished using Legos.
Example One: Andrew Lipson, orginally educated as a knot theorist and a computer programmer, specializing in creating topological sculptures using Legos. Some examples of his creations include a 14-inch high Mobius Strip, a hinged Klein Bottle that shows its two "sliced" Mobius Strips, the tre-foil knot, an ambitious model of the Costa surface (a new complete minimal embeddable surface discovered in 1984), and a model of Escher's "Impossible Staircase." For more information, consult MAA's website for a description of Andrew Lipson's work. Unfortunately, his personal site has been disabled.
Example Two: Andrew Carol is trying to use only Legos to build working-models of Charles Babbage's Difference Engine (which Babage never was able to accomplish due to the lack of precision parts in the 19th century). With the ultimate goal of evaluating 2nd and 3rd degree polynomials to 4-digit precision, his first model was able to could calculate 2nd order differences to 3 digits. His second model, shown on the right, extends to being able to calculate 3rd order differences to 4-digit accuracy. For more information, consult Andrew Carol's personal website.
My Conclusion: Some people have too much time on their hands.