Center for Nutrition Policy and Promotion
Look on the right side of the page, and in the vertical column of links you should see a hyperlink for "USDA Food Plans." Next to that you'll find a link to their latest data PDF. In this case, it's the October '05 Update.
If you're searching for amounts to which you can compare your family's grocery expenses, these PDFs seem like a great start.
2005-06: "How Much Grocery Spending?"