There's a great post over at SmartMoney about oil prices rising to $100 a barrel -- expect:
1. Rising Gas Prices -- it will cost more to drive your car
2. Rising Heating Cost -- it will cost more to heat your home (less if you heat with natural gas)
3. Rising Cost to Fly -- airline tickets will rise
4. Rising Shipping Costs -- transportation costs will also impact the cost of groceries, clothes, etc. because it will cost more to get the product onto the shelf.
Go read the article for details, as well as links for things like cutting energy costs.
If you want to learn more about oil - especially the peak oil issue - then I recommending reading this post over at Mighty Bargain Hunter. As always, MBH gives lots and lots of good info.