Which public company has the largest number of employees?

Wal-Mart Stores Inc., with headquarters in Bentonville, Arkansas, is the company with the largest number of employees in the world. There are currently roughly 2.1 million people employed by the corporation.

Sources:

http://en.wikipedia.org/wiki/List_of_companies_by_employees

http://en.wikipedia.org/wiki/Wal-Mart

More recent employee stat from:

http://www.hoovers.com/wal-mart/--ID__11600--/free-co-factsheet.xhtml