KDE Interactive Geometry Program (KIG) is a great tool for teaching math. Here is a good set of directions on how to do it.
http://www.linuxjournal.com/content/teaching-math-kde-interactive-geometry-program
If that article interests you, but you don’t use Linux, check out GeoGebra which is a program written in Java so it should run on any operating system that supports Java Runtime 1.4.2 or later. You can even do a launch of the program fromt the Web.
http://www.geogebra.org/cms/index.php?option=com_content&task=blogcategory&id=67&Itemid=63
