Great source of cultural work differences from the Canadian government.
The Hofstede Centre - Strategy - Culture -- Change
"Insights into national and organizational culture" by Geert Hofstede, authority on workplace influenced by culture.
Various guides on culture and negotiation for multiple countries
International Business Etiquette, Manners & Culture
Select country guides using Geert Hofstede's Analysis.
Country Commercial Guides (US government)
Free from the U.S. government. Each report is designed to help business people understand the basic of doing business in other countries.
Doing Business in.. (Baker & McKenzie)
The international law firm Baker & McKenzie has free guides to the legal aspects of doing business in various countries.