Count number of identical values in a column

I have a column of several hundred text values, such as "a1" and "a2". I want to find out how many a1's are in that column, how many a2's, etc. How can I do this?

Thanks

HI
List Unique values* in col B (say B2 to B25) and insert the formula
C2=countif($A$2:$A$500,B2)
Drag the formula down
* You can use DATA > filter > advanced filter > Unique records only and copy to another location.
Ravi