Excel

Find Items in one column that are not in another column

   Select the list in column A
   Right-Click and select Name a Range...
   Enter "ColumnToSearch"
   Click cell C1
   Enter this formula: =MATCH(B1,ColumnToSearch,0)
   Drag the formula down for all items in B

If the formula fails to find a match, it will be marked #N/A, otherwise it will be a number.

If you'd like it to be TRUE for match and FALSE for no match, use this formula instead:

=ISNUMBER(MATCH(B1,ColumnToSearch,0))

If you'd like to return the unfound value and return empty string for found values

=IF(ISNUMBER(MATCH(B1,ColumnToSearch,0)),"",B1)