id Software recently has a deal going on where they are offering a dozen of their classic games, plus all the expansion packs, for $69.95 via Valve's online distribution system, Steam. It's a pretty good deal for those who enjoy classic FPS PC games and even includes recent games such as Doom 3. The titles are also available for individual purchase or in smaller compilation packs as well.
Here's a partial listing titles available in the id Super Pack (not including the expansion packs): Commander Keen (episodes 1-5), Ultimate Doom, Doom II, Doom III, Heretic, Hexen, Hexen II, Quake, Quake II, Quake III: Arena, Wolfenstein 3D, and Return to Castle Wolfenstein. It's a good deal for that price, to say the least.