The price of corn, for example, is down 56 percent since July 2008 on the Chicago Board of Trade.
Here is more. I don't in fact think that the financial crisis has improved global welfare. But we are trained to think probabilistically. What is the chance that the gains from lower commodity prices — most of all for poor people who buy food — outweigh the losses from the collapse of world trade and lower overall growth?
Addendum: Here are some related queries.