If you weren't lucky enough to swipe a premature copy of Bioshock from a retailer who broke the street date--I'm looking at you, Toys R Us--then you'll just have to settle for this incredibly detailed free artbook that 2K Games has on their site. Hopefully this, coupled with the recent demo, will prevent your descent into insanity while waiting for the August 21 release date.
The 67-page book entitled Breaking the Mold, gives you an exclusive behind-the-scenes look at the making of the game, along with tons of concept art and commentary from the creators themselves. It is available in two formats, low- and high-resolution, and can be downloaded here.
A word of warning: It's a good idea to skip Ken Levine's foreword at the beginning of the book, because it contains some spoilers that may ruin a few details of the game.