This interactive animation shows the effect of adding a constant to the function.
http://www.yenka.com/freecontent/item.action?quick=ji#

This interactive animation shows the effect of multiply the function by a constant a where a >= 0.
http://www.yenka.com/freecontent/item.action?quick=ot#

This interactive animation shows how altering b in the function
y = sin(bx) changes the frequency/wavelength.
http://www.yenka.com/freecontent/item.action?quick=ou#