The most recent issue of fortune has an excellent interview with Jim Rogers, of Investment Biker and Adventure Capitalist fame, as well as an excerpt from is new book, A Bull in China. Jim saw the start of the current commodities supercycle early (peak oil is just one driving force for this cycle), but it still has a long way to run, in my opinion, as well as Jim's. Almost everything has some dependence on energy prices, because of either the embodied energy, or because if the embodied energy of substitutes. As Jim says in the interview,
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.