What is a number? This interesting site discusses
different classifications of numbers. This site
includes some types of numbers not discussed in
this text, but nevertheless this is a worthwhile
site.
http://www.cut-the-knot.com/do_you_know/numbers.html
Rational Numbers
http://mathworld.wolfram.com/RationalNumber.html
Teaching module on rational numbers for prospective
teachers.
http://jwilson.coe.uga.edu/texts.folder/tirosh/Module.html
This is an interesting enrichment site which
represents rational numbers in an artistic way.
It is entitled, "A Visual Notation for Rational
Numbers":
http://members.tripod.com/vismath7/proceedings/tolmie.htm