I’ve added several GeoGebra files to my Parabolas and Quadratics page. Some are self-explanatory, others will probably only make sense if you download and familiarize yourself with the accompanying curriculum materials.
GeoGebra users may be interested in my use of the very powerful “Sequence” command in creating the trinomial.ggb file. This command allows interactive geometry to go a lot further. (You can not only build sequences of numbers, but also sequences of points, segments, and so on!) Also note the use of Boolean quantities in quad-formula-new.ggb (though that particular file will only be of use to people who are already intimately familiar with my new proof of the quadratic formula.) The use of these features, plus the input line, makes the building of new figures extremely efficient.
As always, I welcome feedback, and if you create Sketchpad or TI or other versions of these, please send them to me. I’ll post them and credit you.