Cotton is a good way to buy oil-- hear me out. Much apparel has been made from synthetics. Synthetics come from oil. So many textile makers are converting back to natural fibers because oil is at an all-time high. So if you want to buy oil, buy sugar [because it is easy to turn into ethanol], or buy cotton. What I'm buying right now is agriculture.
I hadn't thought of this cotton-oil connection before, and it's drawing these connections before others do that makes a great investor. Incidentally, cotton and oil are also connected more directly via the use of oil to make pesticides and fertilizer, and indirectly when land formerly used to grow cotton is shifted to grain production because of rising ethanol prices, but I think the substitution effect Jim talks about is likely to be strongest.