Here you fill find some resources on using Geogebra in your classroom. First, what is Geogebra?
Euclid the Game is a great way for students (and teachers) to get familiar with constructions and Geogebra's construction tools.
Geogebratube is THE place to search for activities and resources for using Geogebra with students. See this 2 min video for an introduction to using Geogebratube to find resources.