Famile Education Network: Measure It! http://www.funbrain.com/measure/index.html
Measuring game in which you have to correctly guess the amount being measured, it has both metric and imperial options and three difficult levels.
Kids Health: Bones http://kidshealth.org/kid/body/bones_noSW.html 'The Big Story on Bones' that gives information about all the major bone groups in a series of fun articles. There are tips on caring for your bones, as well as clear explanations about each bone group.