There are several approaches possible depending on what you want to do exactly.
A fairly simple method:
Define a summary field "Countfld" as count of your drop down field.
Create a list view layout and delete the body.
Add a sub summary part "when sorted by your drop down field"
Put Countfld and your drop down field in the sub summary part.
Enter browse mode and sort your records by the drop down field.
If you are using FMP 10, you will see a list of each value in drop down field with the number of records for that value.
If you are using an older version, preview the layout or print it and you'll see the list of values.