Geometers Sketchpad has to be one of the most efficient and productive learning tools available for my 8th grade geometry class. Last week we went into the lab to study the areas of parallelograms, triangles, and trapezoids using this program. We were able to manipulate the shapes using a simple drag tool to see that as long as the base and altitude of a shape stays the same, then the area will also be the same. This is quite a difficult concept to grasp, and even more of a difficult concept to picture, but Sketchpad does a wonderful job of allowing the students to quickly and easily develop an understanding.
I really feel like every lesson could be taught using this program. However, teaching planning time and lab availability would make this extremely difficult. What if the students all had laptops, or IPads???? Man, oh man, the possibilities would then be endless. (I would still have to somehow think of ways to incorporate that technology into my other classes though.)