http://en.wikipedia.org/wiki/Peak_oil is a great place to start.
Expert opinion is that oil production has peaked or will peak in a few years. This will be very bad for developed economies if nothing is done, and nothing is being done.
I don't agree with the Doomsday scenarios some follow but make no mistake, oil production will peak soon and then go into decline, and fairly bad economic effects will be felt around the world.