http://www.usda.gov/oce/commodity/wasde/ – World agricultural supply-demand estimates from the USDA, monthly
http://www.ers.usda.gov/publications/whs-wheat-outlook/ – Wheat outlook based on WASDE report above
http://usda.mannlib.cornell.edu/MannUsda/viewDocumentInfo.do?documentID=1048 – Crop progress report, weekly
http://usda.mannlib.cornell.edu/MannUsda/viewDocumentInfo.do?documentID=1079 – Grain stocks report, quarterly