GOG.com

GOG.com, formerly Good Old Games, is a DRM-free digital video game distributor that originated with re-releasing old games, but has since expanded into new releases as well. Since, GOG.com distributes games published by Bethesda Softworks, including id Software's titles.

Catacomb games

 * Catacombs Pack includes all Catacomb games produced by id at Softdisk ($5.99)

Classic Doom games

 * The Ultimate Doom ($5.99)
 * Doom II, the Master Levels, and Final Doom ($9.99)

Quake

 * Quake: The Offering ($9.99)