However, the big question is: What will humanity do to deal with this crisis? There are many alternatives in the way of energy resources, but 70% of all oil is consumed by automobiles, airplanes, trucks, etc. With diminishing oil resources, gas prices will spike to well over $7 / gallon and many airliners will go out of business because of the high jet fuel prices. With all of these domestic problems in developed countries (and also big developing countries like India and China), a great deal of tension will form between the large consuming nations and the producing nations, leading to "oil wars" (some point to the Iraqi War as a preindicator of this).
The world is incredibly unprepared for this crisis (probably to be one of the biggest in human history) and will almost definetly lead to a large-scale global recession of some kind.
It is also predicted that the,currently, enormously popular suburbs of the world will turn into the global slums as people will be unable to pay $100 USD+ per day on fuel.
Some people point to hydrogen cars, but that technology is far from being developed enough to be of use in the near future (maybe by 2015?) and biodiesel supplies are far from being ready for widespread use. Also, non-conventional supplies of oil are much harder to extract and utilize, and even though they could help keep some moderate oil supplies, it would still be far from being enough for widespread global use and distribution.
Is humanity capable of overcoming these future problems? The governments of today are making small but largely ineffective efforts to curb this future crisis (The U.S. just passed its first "suggested" gas efficiency for cars~ I think), so most people are looking to a much more difficult "market solution". With a market solution, the skyrocketing global prices of oil will inspire wide-spread investment in "green" technologies to help replace oil, but the problem is that many of these "green" technologies require oil for their research and development phases.
So, what will humanity do to overcome this?
A few oil based products:
Fertilizer (oil based fertilizer and machinery allowed for the "Green Revolution" that allowed many people to move to the cities, and drastically improved the amount of food available. Some fear that a global oil crisis may lead to mass starvation.
Plastic (... self-explanitory)
Gasoline
Jetfuel (no more airplanes? more efficient engines are being made that could possibly utilize the more expensive non-conventional oil resources to allow for the coninuation of flight ^^... increase in ticket prices?)
There are alot more but I am tired and weak from my wisdom-teeth removal

Could there be replacements to oil?
Possible conversion of coal into oil
~(?) I read on the new york times about conversion of pig feces into oil O.o (not sure if this could ever be a major replacement)
Non-convention oil resources: tar-sands, and other things
So what are your ideas and comments? (sorry if I didn't write this well enough and my ideas are scattered... I'm tired and my mouth is really soar

This was mainly based on the Hubbert Peak Theory which you can read more about here: http://en.wikipedia.org/wiki/Peak_oil