GeoGebra

GeoGebra is free and multi-platform dynamic mathematics software for learning and teaching. It has received several educational software awards in Europe and the USA.

Free Open Source Mac OS X Windows Linux Android Android Tablet iPad Web

the geometers sketchpad

Sketchpad® Dynamic Geometry® software gives students a tangible, visual way to learn mathematics that increases their engagement, understanding, and achievement. And it's not just for geometry.

Commercial Mac OS X Windows

Lybniz

Lybniz is a simple and very easy to use mathematical function graph plotter written in Python and GTK. Expressions are entered in Python syntax.

Free Open Source Windows Linux