Due to my job and other factors (like a relevant game being demo'ed for the first time), this issue is a bit late, just under half a month off ;) This will only cover stuff created during July.
Classic Doom
Doom II instruction manual
GT Interactive Software
Skeleton map articles for all of the PlayStation Doom maps (thanks Xymph)
Hexen
Hexen: The Official Strategy Guide
Merchandise
Thrustmaster Doom Edition headsets