
Geogebra
GeoGebra is a free dynamic mathematics software package for all levels of education that joins arithmetic, geometry, algebra and calculus. It offers multiple representations of objects in its graphics, algebra, and spreadsheet views that are all dynamically linked. 
Project Maths Documents
This 5 page pdf document gives a very short introduction to the Geogebra Package. It takes you through creating an interactive version of a theorem whilst explaining the different features of Geogebra along the way.
This 8 page pdf document takes you through constructions of parallelograms, Equilateral Triangles, Isosceles Triangles, Enlargements, Centroids of Triangles, Circumcentre and Circumcircle of Triangles and Incentre and Incircle of Triangles.
This 7 page pdf document looks at: The Coordinate Plane, Line segments, Lengths, Midpoints, Points of Intersection, Slopes of Lines, The Use of Sliders for Dynamic Line Presentations, Drawing Triangles, Finding Areas, and Translations.
This 8 page pdf document looks at: Demonstrate the Defintion of a Circle, Plotting Dynamic Circles, Intersection of Lines and Circles, Equations of Tangents to Circles, Transformation of the Circle, and Examining Theorem 20.
This 6 page pdf document looks at: Plotting Trigonometric Functions, Changing From Radians to Degrees, Plotting Dynamic Fuctions of y = asinbx and y = acosbx, and Creating a Dynamic Worksheet.
Links to Other Websites
The above website will take you the offical Geogebra website, where you can download the software for free.
Get help and support from other Geogebra users from all over the world.
Regional Centre for Excellence in Mathematics Teaching and Learning have also developed resources for Geogebra. The resources can be accessed at the above address.