Links

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

Clock arithmetic and modular arithmetic
http://www.shodor.org/interactivate/discussions/morerem.html

This site gives a nice introduction to modular arithmetic and leads to the next section on cryptography if you following the links on the site.
http://www.math.rutgers.edu/~erowland/modulararithmetic.html

This site is a nice interactive site which deals with arithmetic (mod m). Do not be frightened by the notation, the arithmetic table at the bottom is interesting
http://www.cut-the-knot.com/blue/Modulo.shtml

Is there really such a thing as "infinity"?
http://www.math.toronto.edu/mathnet/plain/answers/infinity.html