Links

Videos

Introduction to derivative -  (time: 8:44) 
http://www.youtube.com/watch?v=zgiNciB3qhw

History

This is one of the best all around sites that I have found. It is titled "The MacTutor History of Mathematics Archive."
http://www-history.mcs.st-and.ac.uk/~history/

This is an award-winning site that links to all sorts of mathematics information.
http://archives.math.utk.edu/

Reference Topics

This is a more advanced site than we need for the introduction in this book, but check out the following choices on this site:
"Secants and tangents"
"Zooming in on a tangent line"
http://www.math.psu.edu/dna/graphics.html