tail lights not working

I have an 89 super charged cougar and recently discovered the following problem:

I have headlights and brake lights but no parking lights or tail lights.

I checked the fuse box in the car and the tail light fuse was blown. I replaced it and it immediately blew again. I checked the trunk for a loose connection and found none. I checked the fuses under the hood and they all looked fine. Anyone have any suggestions or other places I should check before I try to track down a loose or shorted out wire. Anyone know what the fuse that keeps blwoing suggests?