NOAA
Noaa: Free Fall Determination of Newtonian Constant of Gravity
Descriptions of an experiment performed by geologists to determine the Newtonian constant of gravity, or "G". Highly sophisticated reading.
Frostburg State University
General Chemistry Online: Faq the Mole Concept
This FAQ site over general chemistry concepts presents the question: "Why are moles used?" It explains what moles are and how they can be used to count molecules and how grams can be turned into moles.