GeoGebra
When you enter into the world of GeoGebra, for free, you quickly find out about the incredible support mechanisms created from interested users of all levels from across the globe.
GeoGebraWiki is a searchable pool of free teaching materials created with GeoGebra currently supporting 28 languages. Anyone can upload their resouces to the Wiki.
GeoGebra Forum is a searchable Q & A site for all matters GeoGebra, be they questions about usage or technical details. Currently the Forum hosts 22 languages.