Learn Geogebra
GG classic tutorials (demos + step-by-step)
GG Calculus (lessons)
GG Algebra 1 (lessons)
GG 3D calc+precalc (lessons)
GG Trig (lessons)
Geogebra 5.0 online manual (include links to many tutorials)
Vast Collection of Tutorials (some video)
GeoGebra 4.4 Manual (pdf) (older version but still useful)
[Extensive] List of Geogebra commands