Links

Videos

Math in Nature - Fibonacci (time: 5:01)
http://www.youtube.com/watch?v=g_L1hCSR0s4

Phi and the Golder Ratio (time: 4:08)
http://www.youtube.com/watch?v=326dzCPfnQk&feature=related

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

A discussion some of the historical proofs of the Pythagorean theorem are listed.
http://www.cut-the-knot.org/pythagoras/index.shtml

These sites provide some information about the Great Pyramid.
http://buildings.greatbuildings.com/Great_Pyramid.html

For a more complete (and a bit more advanced) treatment of the sine and cosine functions, see this site:
http://www.hofstra.edu/~matscw/trig/trig1.html