Use Excel's Advanced Filter to delete duplicates in a list

When you need to find the unique entries in an Excel list, the quickest way to locate them is with the Advanced Filter. For example, you have a list of cars sold by date and location. You would like to see a listing of the cities where the cars were sold. Because you sold multiple cars in a number of cities, the data in the City column contains a number of duplicates. To produce a city list without duplicates, follow these steps:
Select the City column.
Go to Filter Advanced Filter.
Click in the Copy To Another Location text box, then click on a cell in the same worksheet where you want to locate the new list.
Click the Unique Records check box.
Click OK.
Excel will list the unique values found in the City column at the designated location.
Source: http://office.microsoft.com/en-us/excel/HP052001781033.aspx