Links

Videos

Area (time: 4:15)
http://www.youtube.com/watch?v=9WnmYezOdRk

Area vs. Perimeter (Time: 7:15)
http://www.youtube.com/watch?v=2jUNC2N0Uxw

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/

These sites are dictionaries of units of measurement.
This site has many nice links to other sites.
http://www.unc.edu/~rowlett/units/index.html

Reference Topics

The international system of weights and measures (by Russ Rowlett) can be found here:
http://www.unc.edu/~rowlett/units/sipm.html

The book Flatland (suggested as a book report at the end of the chapter) can be found online at:
http://www.alcyone.com/max/lit/flatland/