Other helpful websites:
Online Graphing Calculator:
http://my.hrw.com/math06_07/nsmedia/tools/Graph_Calculator/graphCalc.html
www.math.com/
www.webmath.com/
www.mathforum.org/dr.math/
www.mathpower.com/
www.freemathhelp.com/
http://www.media.pearson.com.au/schools/cw/au_sch_rogers_mm34_1/int/trigg.swf