United States Department of Agriculture
The United States National Agricultural Statistics Services publishes monthly statistics on dairy cow inventory, milk production, milk per cow and other related information. For up to the minute information, go to the National Agricultural Statistics Service website.
Contains a wealth of information for the dairyman including information on top ag commodities, top 15 dairy counties, regional milk production information and more.
Colorado State University Extension has a lot of good resources on their recently updated extension website portal for Dairy. http://articles.extension.org/dairy_cattle
National Dairy Council
Offers information for both professional and consumers on the benefits of dairy products.
U.S. Farmland Statistics
The 2007 Agriculture Census.
Association of American Feed Control Officials