Peak Oil is the point at which global oil producution reaches its maximum, and from there on it's all downhill. With oil demand continuing to grow, the only consequences can be shortages and rapidly increasing prices. Peak Oil is predicted by some (based on experience and scientific analysis) to occur in 2010.
An excellent site on this subject is http://www.powerswitch.org.uk
It might make you think, it might make you worry; but if we have an understanding of what the likely problems will be, we can at least prepare for them.