While I don't believe that Peak Oil will be the end of civilization and bring about a new Stone Age, I am concerned about rising oil prices triggering a serious and prolonged depression.
To get a sense of what that might be like, take a look at this 45 minute documentary on how Gypsies survive in a shanty town outside of Belgrade. It's called Pretty Dyna. These modern day road warriors have found a means by which to eke out a subsistence level life by salvaging old car wrecks and breathing new life into them. Many of their vehicles would not be out of place in Mad Max II.