so you're new to portal (2007)/portal 2 (2011)
comics
required reading: lab rat and there are a couple of other, shorter official comics
turret lullaby
randolph the red-nosed turret (preserved on portalwiki)
videos
thinkwithportals.com has most of the ad shorts in one place, but not included there are
portal is free
aperture science romance safety compliance guide
perpetual testing initiative
audio
the portal 2 soundtrack is free online!
glados and cave johnson both have dota2 announcer packs
"don't say goodbye" is an unused glados song that ellen mclain WROTE
apocrypha
aperture desk job is free on steam
portal 2: the final hours is $2 and worth it
significant appearances in both poker night 2 and lego dimensions (including another glados song)
the portal ARG and potatofoolsday ARG
concept art!! (rip portal 2 art book, I will never be over you)
AND you can't forget the old aperturescience.com (archived by valve, thank god) you can look up commands to navigate it but I'd start by trying "help"
I KNOW this isn't everything, I haven't played the VR stuff and don't even know where to start with it, feel more than free to pile on
the cut lines! oh my god glados's cut lines! (check out the "evil again" section, you're welcome)
cave had cut lines too, many of which got recycled into lego dimensions, and the conversation with glados is a clear predecessor to his fate in desk job
and wheatley has some cut/alternate stuff, plus his tf2 cameo as the ap-sap
also @the-dangerous-mute-lunatic reminded me portal2sounds.com exists, every sound file from the game, searchable, super handy
