I've used that program before and it's really quite good.  Very simple interface.

Another good graphing tool is www.desmos.com.  It's fextremely useful if you want to make sliders.  For example, if you wanted to show students what the variables do in y=a(x-h)^2+k do, this is a fantastic choice.  You can quickly and easily make sliders for a, h and k and move them around to see what the effect is on the graph.  Also, it's also all online so you don't have to download anything to use it.