MoMath (Museum of Mathematics http://momath.org/ ) has a great feature called Math Monday. One of my favorite activities presented in this feature is mathematical constructions with crackers. Here is an illustration of a 3-4-5 right triangle with Triscuit crackers:
The number of crackers in the two small triangles (9+16) equals the number of crackers in the large triangle (25).
They also illustrate the Pythagorean relationship with Cheeze-Its http://momath.org/home/math-monday-03-15-10/
You can follow MoMath on Twitter (@momath).