Forbes, State Estate Taxes Loom as Big 2011 Issue, by Ashlea Ebeling:

Despite the new and generous federal estate tax exemption of $5 million per estate and $10 million per couple, many less wealthy families still have to plan for estate taxes–state estate taxes that is. …

21 states and Washington, D.C., have state estate or inheritance taxes in place for 2011. … Thirteen states and Washington, D.C., have estate taxes only. Typically, these taxes exempt $1 million or less per estate and carry a top rate of 16%. Six states levy only an inheritance tax, with the rate depending on the relationship of the heir to the deceased and the taxes kicking in, in some cases, on the first dollar of bequest. New Jersey and Maryland levy both estate and inheritance taxes.