itch.io - An online game marketplace and community.
Playfire - Playfire is the global community for gamers.
GOG.com - DRM-free game store, selling both new and old titles. No clients required.
Gaikai - Gaikai is a company which provides technology for the streaming of high-end video games.
GnuPlot - Gnuplot is a portable command-line driven interactive data and function plotting utility.
Parsec - Streams games locally or over the internet