Here is the collection of business directories links.

BigYellow
Searchable online business yellow pages directory.

Crunchbase
Crunchbase provides a directory of companies plus investors and funding information.

Dun & Bradstreeet
D&B provides a subscription-only database which contains information about millions of companies.

Financial Times
FT.com provides regular financial news and anyalysis, feature and a business directory.

Hoovers Online
Hoovers provides a comprehensive directory of business listings which contain contacts, profiles and recent news articles.

HowToWeb: Internet Business Resources
A collection of links to online business publications and resources.

Open Directory Business Directory Links
Links to hundreds of online business directories.

Yelp
Yelp provides information and reviews about local businesses, including services, retailers and restaurants.