Q. Sales tax rates information

United States:

Sales Tax Rates
Lists the sales tax rate and range of local rates for each state.

SalesTaxSupport.com - Sales Tax by State
Shows sales tax rates for each state and the local rules defining which transactions are taxed and when out-of-state sales have a local connection (nexus) that can be taxed.

Go also to State Sales Tax Rates - The Sales Tax Clearinghouse

European Union:

European Union Sales Tax Rate | VAT

Worldwide:

KPMG Taxation of International Executives 
KPMG member firms have produced a series of summaries titled Taxation of International Executives. These summaries cover relevant income tax and social security rates, together with the key aspects of the tax legislation relating to expatriate employees working in these countries. In addition, planning opportunities, capital taxes and local taxes are also covered, thereby providing useful overviews of the issues that can affect employees on foreign secondments or assignments.

PwC Worldwide tax summaries online
Summarizes key elements of corporate and individual taxes in 151 territories  worldwide, covering tax rates and major features of the tax laws.