Reverse-411.net is the original and most complete index of online phone books, with links to Yellow Pages, White Pages, Business Directories, email addresses and fax listings from over 170 countries all around the world.
This is a great reverse look up for businesses in US.
Reverse-411.net is a one-stop shop for more than 11 million email addresses, telephone numbers and Web sites from around the world. For business contacts in US this is the site. Searchable by product, name of company, or service.