Links

Video:

Irrational Numbers (time: 2:23)
http://www.youtube.com/watch?v=oORCAz-V_Bg

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/

The History of the Decimal Point table mentions the following people, and here are some links in order to find out more about them.

Stevin:
http://www-history.mcs.st-and.ac.uk/~history/Mathematicians/Stevin.html

Viéte:
http://www-history.mcs.st-and.ac.uk/~history/Mathematicians/Viete.html

Kepler:
http://www-history.mcs.st-and.ac.uk/~history/Mathematicians/Kepler.html

Napier:
http://www-history.mcs.st-and.ac.uk/~history/Mathematicians/Napier.html

Oughtred:
http://www-history.mcs.st-and.ac.uk/~history/Mathematicians/Oughtred.html

Ozanam:
http://www-history.mcs.st-and.ac.uk/~history/Mathematicians/Ozanam.html

Reference Topics

The most famous real numbers that are not rational are the numbers pi and e. However there are many interesting constants in mathematics, as described at the following site:
http://algo.inria.fr/bsolve/

This site answers some questions about numeration systems:
http://www.math.toronto.edu/mathnet/answers/numbersystems.html

The number 0, the additive identity, is the subject of many web sites:
http://www.math.toronto.edu/mathnet/plain/questionCorner/zeroorigin.html

http://mathforum.org/dr/math/problems/purpose_zero.html