A tax haven is a state or foreign government, most often offshore, which allows an individual or corporation to "hide" money, in a technically legal fashion, from their nationality's tax system and therefore avoid paying taxes on that money.
Also certain states, such as those in the American Redoubt have no sales tax (Oregon and Montana), or no income tax (Wyoming - see Free State Wyoming) or very low property tax (Idaho) and are considered to be more "free states" for that reason and others such as Second Amendment gun rights concealed carry and open carry freedom
Taxes and Cost of Living
Before making a strategic relocation or "vote with your feet" move to another state or country, be sure to research the various tax rates and the relative cost of living. These web sites might prove useful:
Overall Tax Burden by State: http://www.taxfoundation.org/files/burden_by_state-2007-04-04.pdf
State Income Tax Rates: http://www.taxadmin.org/FTA/rate/ind_inc.html
State Sales Tax Rates: http://www.taxadmin.org/FTA/rate/sales.html
Cost of Living Comparison: http://www.relocationessentials.com/aff/www/tools/salary/col.aspx