http://moneycentral.msn.com/content/Taxes/P80242.asp

"With corporate tax receipts at 20-year low, the GAO takes a look through the books and finds 94% of all U.S. companies paid less than 5% -- and 61% paid nothing at all."

http://www.ctj.org/corpfed04an.pdf

This report chose 275 corp's and lists the:
"82 Companies Paying Zero Tax or Less in at Least One Year, 2001–2003"

Some of the largest in the world are on the list.