Here is a pretty good article on gas prices. It has some flaws, but is still worth a read. Check out the article's comments for coverage of the flaws. Some of the commentators miss one of the author's points. He is not focusing on why the price of gas has gone up over the last 5 years. He is asking why, based on what the price of gas was in 1950 and considering inflation, taxes and demand, is gas not more expensive now than it actually is.
Here is an article on agricultural commodity futures market volatility. My expertise regarding commodity futures is limited. I have a couple of theories as to what could be contributing to this volatility (increased demand leading to exaggerated responses to new information or a speculative bubble in some commodities), but I have no idea if either theory has any validity.