I just picked up a set of black Weathertech mats for my 987. They were about $60 bucks, and they fit the footwell perfectly. (cut to fit your make and model) It is a nice, heavy rubber mat that traps all of the dirt, snow, and water that you might bring into your car. I wish Porsche made a good OEM rubber floormat, but this set is probably just as good as what the dealer would give you.
http://www.weathertech.com/
That's my $.02