Avogadro's Hypothesis
I liked this sight (and got all the questions correct- yay!) Although, when I followed the 'scientific revolution' link, I had to look up 'phlogiston theory.' Guess I don't need to know elements proven not to exist- but it's interesting history!
It's incredible that Avogadro was not recognized for all he contributed in his lifetime, because it certainly was a contribution! Chemistry flourished after people figured out the difference between atoms and molecules, and how to measure their respective weights. And Mendeleev was able to conceive our handy periodic table.
Thanks Avogadro!

Checking out the Mole
This site was a big block of words (graphics usually help with chemistry digestion) but it did explain everything I wanted to know about moles pretty clearly. And it piqued my interest in the chemistry of glaze design work in the ceramics industry too.