Introductory Geogebra Lesson
I did this with my students about a week ago: http://scottfarrar.googlepages.com/geom2009
Previous Knowledge: students have copied and bisected angles and segments before "IRL" using compasses and straightedges.
It went very well for a "first time" on computers this year. The versions of the files I initially used did not limit their tools, but I have now changed the mathlets: you are limited to Euclidean constructions via compass, straightedge and points/intersections.
The fourth mathlet is too hard. The first three took most of my students about 20-40 minutes to get through. So I definitely need a fourth problem that is relatively simple, yet exposes them to something new in Geogebra.
"Free exploration time" works for some students, but if they are that interested, they can do it at home on their own computers. I'd rather have an engaging mathlet.