The National Agriculture Library has a "Food and Nutrition Information Center" and food-related information in its online catalog, both accessible from the NAL Web site .
Food definitions and explanations, there are many good food encyclopedias (for titles, search the New York Public Library online catalog.
The Food Timeline explains how human cuisine has developed over the centuries.
Additives: Food additives are listed, described and discussed in the Food Chemicals Codex by U.S. Pharmacopeia (USP-FCC). See also "FDA Petitions," below.
FDA Petitions: Food Additive Petitions, Color Additive Petitions, Generally Recognized as Safe Petitions and other FDA filings and documents can be purchased from FOI Services.
Codex Alimentarius: The Codex Alimentarius is set a food safety standards set by the Codex Alimentarius Commission. The Codex is held in many large libraries and is posted in the Official Standards section of the Commission's Web site.
The main documents for interpreting the Codex are the "Reports" issued by the Commission and its committees. Recent reports are posted in the Meetings and Events section of the Commission's Web site.
U.S. input to the Codex is handled by the U.S. Codex Office, a division of the U.S. Department of Agriculture in Washington (202-205-7760). If you have questions, try calling the Codex Office at 202-205-7760.
Dietary Supplements: Dietary supplements are substances that are eaten but not "represented as a conventional food or sold as a sole item of a meal or the diet." They can be vitamins, minerals, amino acids, herbs, etc. The FDA does not regulate their safety, but it does regulate their labeling. You can find information about supplements (what they are, who they are made for, how they are labeled), see the Dietary Supplement Label Database (DSLD).
Nutrition: The classic reference work on nutrition is Dietary Reference Intakes: The Essential Guide to Nutrient Requirements (The National Academies Press). The Nutrition Source posts information on healthy eating according to contemporary science.
Prices: For information on the historic price of food in the U.S. see the Food Timeline's FAQs: historic food prices page.
Recalls: The Food Safety and Inspection Service posts lists of food recalls issued by the U.S. Federal and state governments. The FDA posts guidance on appropriate recall procedures for food suppliers. European Union food recalls are posted in Europa's Rapid Alert System for Food and Feed. Canadian food recalls are posted on the Canadian Food Inspection Agency's Food Recalls and Allergy Alerts page.
Restaurants: Lists Online links to lists of top restaurants. Zagat.com provides survey-based restaurant reviews for major urban areas. Some cities post databases that summarize the results of their restaurant inspections, including New York, Denver, San Francisco and Washington D.C..
Warning Letters: U.S. Food and Drug Administration Warning Letters are posted on the FDA Web site and through a number of Thompson's subscription products, including the FDA Enforcement Manual.