Walkers Mammals of the World lists 7 subspecies, other authors up to 14.
Here is a link to Schreber's orignial description of the nominate subspecies
The Mammals of Suriname - Google Book Search
The only other description I can find up to now is for P.f.chiriquensis from Costa Rica.
grey with a white-tipped tail and white paws. Underside tawny-yellow or buff, muzzle brown-black and hairless.
If you are in no hurry I have ordered a copy of The Handbook of the Mammals of the World volume 1 Carnivores, due to be published in March 2009. This will have a description of all the subspecies the authors consider to be valid. The trouble is people seldom agree on what is valid and what is not.
Walkers list the following
P.f.flavus (Schreber 1774)
P.f.chapadensis J.A.Allen 1904
P.f.chiriquensis J.A.Allen 1904
P.f.megalotus (Martin 1836)
P.f.meridensis Thomas 1902
P.f.modestus Thomas 1902
P.f.nocturnus Wied-Neuwied 1826