Here are all the materials from a GeoGebra workshop that I presented at a Summer Math Institute this summer, along with some bonus videos. Special thanks to Guillermo Bautista of Mathematics and Multimedia and to all the contributors to GeoGebraTube for all the great materials. Any material posted here is free for anyone to use; shout-outs and linkbacks appreciated.
Links to Selected GeoGebra Worksheets:
1. Tangents to a Circle
2. Inscribed Angle Intercepting Semicircle
3. Congruent Chords in a Circle
4. Central Angle of a Circle
9. Isosceles Trapezoid
10. Triangle Exterior Angle Sum Theorem
11. Maximum Volume of a Box (calculus)
12. Car Race (animation)
13. Box Plot (with Spreadsheet View)
The first two videos show you some things you can do using already-existing GeoGebra worksheets on geogebratube.org; you don't have to download or install GeoGebra, all you need is a browser and an internet connection.