Links

Video

Perimeter  (time: 6:18)
http://www.youtube.com/watch?v=XgDC1qb48ps

 

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

Perimeter is introduced at this site, along with some practice problems.
http://www.mathgoodies.com/lessons/vol1/perimeter.html 

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/

A very useful dictionary of units of measurement is found at this site:
http://www.unc.edu/~rowlett/units/index.html