I really enjoyed the original Valve's Portal BBS you could dial into Aperture Science and read on the history. The writers at Valve really wrote some great silly backstory about a shower curtain company developing quantum portals, as some sort of tool to get in and out of showers. I'm not sure that's cannon anymore though.
I think that still is (per Portal 2), but some of the original details aren't – like how Cave Johnson poisons himself, and how much his excellent decision-making was influenced by said poisoning.
