Kevin Drum has an interesting post on this subjecting, citing an ExxonMobil report that oil production in non-OPEC countries will peak in the very near future. The upshot is that all future demand growth for oil (which ExxonMobil underestimates) will have to come from OPEC (i.e. the Middle East and Venezuela). Given that OPEC reportedly has very little spare capacity (they're pumping as fast as they can pump), this means that we're likely to see significant price rises as demand begins to exceed supply.
Unlike some, I don't believe this spells the end of civilisation as we know it. However, the end of cheap oil is going to mean change - and fairly significant change at that. On a personal level, driving cars will become much more expensive - meaning that we will need to either get far more fuel efficient vehicles, start using public transport more heavily, or live closer to where we work. International air travel, which relies totally on hydrocarbons, will become more expensive as well, and the age of the cheap holiday or business trip will probably end. We will, in other words, become more local, more tied to one place, and we won't have much of a choice about it.
On a global level, the changes will be far more mixed. Price rises will probably not mean energy crises - the world has been moving away from burning oil for electricity in favour of coal and natural gas since the first oil shock. But higher transport costs will tilt the balance between our current globalised economy and local production. It won't spell a universal end to international trade in physical goods - bulk non-perishables will be relatively unaffected - but the rising cost of airfreight may make the shipment of some types of good simply uneconomic. Companies, and possibly even economies, will fail as a result. And as a country which depends on agricultural exports to make our way in the world, we may very well be one of them.
(On the plus side, it won't all be bad. Increased localisation may reverse the trend of company HQ's relocating across the Tasman, and will almost certainly result in businesses and branch offices returning to our suburbs and small towns. Which should cushion the economic impact somewhat...)
What can we do about this? Pretty much nothing. It will happen; the only question is the timing. The best we can do is plan now to reduce its impact, while hoping for economicly viable fusion power...