(Fortune Magazine) -- 1. Exxon Mobil

Book: The End of Oil: On the Edge of a Perilous World, by Paul Roberts. Are Exxon's days numbered?

Web: exxonmobil.com; topix.net/forum/com/xom

2. Wal-Mart

Book: The Wal-Mart Effect: How the World's Most Powerful Company Really Works--and How It's Transforming the American Economy, by Charles Fishman. It's not just a business anymore.

Web: walmartfacts.com; walmartwatch.com

3. Royal Dutch Shell

Book: A Century in Oil: The Shell Transport and Trading Company 1897--1997, by Stephen Howarth. An authorized history of the Anglo-Dutch giant.

Web: shell.com; royaldutchshellplc.com

4. BP

Book: Oil Titans, by Valerie Marcel. With contributions by former BP advisor John V. Mitchell.

Web: bp.com

5. General Motors

Book: Billy, Alfred, and General Motors: The Story of Two Unique Men, a Legendary Company, and a Remarkable Time in American History, by William Pelfrey. A biography of the company's two giants.

Web: gm.com; fastlane.gmblogs.com