I doubt there are any super geeks in this thread but just in case:
www.somethinginthesea.com
Gives some back story about Rapture and the beginnings of it. It's told through the eyes of a guy named Mark Meltzer who's daughter gets kidnapped and taken to Rapture. Interesting stuff, especially since you find Mark Meltzer audio diaries in the game.
Haha, I've been following that site since October 2008, which is when it launched. Yep, I'm a super geek.
For anyone who's interested...
It started when girls along the Atlantic coasts started vanishing. Then there were sightings of this 'tall, thin, looking thing with a red light' (now commonly known as a Big Sister) that came from the ocean and was later discoverd to be the one taking the little girls. Mark Meltzer was one of those guys who just gets obsessed with finding the truth and so he set himself out to capture it. Well, the Sister came and attacked him, leaving him with a broken leg. I'm not sure if it was later that night or on a later night, but his daughter Cindy disappeared. He believes that that 'thing' followed him and took his daughter. He became so obsessed with finding his daughter that his wife left him because 'he was going crazy'. There was a detective that was helping him out and stories about this guy named Oscar Orrin Lutwidge, a.k.a. O.O.L. (He's the guy who supposedly sent those 'invitations' to 'finding true Rapture' to people, which were later revealed to be an official invitation to the launch party). Well, this O.O.L. guy had lived in Rapture and talked about it but people dismissed him as a nut case. Mark believed him but never found him.
After that, I missed a few months of it because I didn't internet, but it was all mostly searching for this Oscar guy and some other people.
Towards the end, he finds out about Rapture and decides to take matters into his own hands and sets himself out for Rapture. He gets on a boat with a guy who had 'shipped goods' to the coordinates of the city. It was speculated that he was the guy who helped Atlas/Fontaine smuggle all the shit you see in the first game. Last thing I heard, he was on this boat. When I played the game, I found his diary where he talked about 'barely making it into the city'. Have you finished the game? Not really a spoiler, but did you get to come across him?