GnuPlot - Gnuplot is a portable command-line driven interactive data and function plotting utility.
GOG.com - DRM-free game store, selling both new and old titles. No clients required.
GeoGebra CAS Calculator - Free online algebra calculator from GeoGebra: solve equations, expand and factor expressions, find derivatives and integrals
itch.io - An online game marketplace and community.
Geometry Pad - Geometry Pad is a dynamic geometry application for iPad and Android tablets.
GeoGebra - GeoGebra is free and multi-platform dynamic mathematics software for learning and teaching.