IT Tools for Maths
Here's 2 IT Tools for Maths. They are Graphing software and it's free. Very good for plotting and teaching of graphs. However, I think they are not compatible with Mac OS. I've used both, sometimes I prefer using Graphs as it gives a cleaner background.
1. Graphmatica: http://www8.pair.com/ksoft/
2. Graphs: http://www.padowan.dk/graph/