An international treaty was signed May 20, 1875, providing for the establishment of an International Bureau of Weights and Measures. Headquartered in France, the task of the BIPM is to ensure world-wide uniformity of measurements and their traceability to the International System of Units (SI).
Want to compare the sizes of different things? Check out Sizes.com! Browse common furniture dimensions, clothing sizes, tools and hardware, food and drink, natural objects, manmade materials, sports equipment and playing fields, etc. (Note: While this is a very interesting site, if you are looking at it with your children you may want to steer clear of the “People” tab under which they measure certain body parts.)
Also, on their homepage you can get a random quote related to the concept of measurement. (Keep refreshing the page to see more quotes.)