Yahoo did a great blog post predicting an online boon to the rising gas prices: http://www.ysmblog.com/blog/2008/07/01/high-gas-prices/.
There are days that I will not drive to certain restaurants anymore because I feel it is wasting gas if they are too far away. I happen to live very close to a mall, but I totally agree with Yahoo. If a can save a trip to a specialty store, it makes sense to buy online. The only caveat to their prediction is increasing shipping costs due to the increasing fuel costs.
Online marketing should be very strong for the 2008 holiday season regardless of high fuel costs. Fueling the fire of high fuel costs (intended pun) may be a nice way for SEOs and SEMs to more easily sell their services this year!