We have a SuperCheats.com exclusive game guide for Bioshock here:
http://www.supercheats.com/guides/bioshock/

There is a full walkthrough with screenshots and well as an overview of the game's weapons and enemies.

There is also a guide for all 122 Audio Diary Locations, Tonics list and weapons upgrade. All achievements are also listed.

Reaching Atlas Fontaine's Penthouse:
The code which is in an Audio Diary is 5744.

Hitting the Jackpot at Slot Machine:
Before you start playing the slot machine save the game and then keep reloading your saved game until you hit the jackpot.

Unlock Alternate Endings:
The ending you get depends on how the Little Sisters were treated during the game. The 'bad' ending will play if more than one Little Sister was harvested and the 'good' ending will play if no more than one Little Sister was harvested and the rest were rescued.