We got our Prius with the 5-piece carpeted mat set, but I'm also shopping for all weather mats for the floor & trunk. The two products that have popped up most frequently in my searches have been the WeatherTech and ExactMat mats & cargo liners.
I've read good things about the ExactMats, especially about how well they fit. They appear to be made of that same heavy clear plastic with the little spikes on the bottom used under office chairs to protect and make it easier to roll the chair on carpeted floors. The main complaint seems to be that this type of mat does not have the channels along the perimeter to prevent water & debris from spilling onto the Prius' carpeting. Metro Toyota has these mats here:
http://www.metrotpn.com/ProductDetails. ... rtIndex=12
The WeatherTech mats are made from thick, flexible rubber and have the deep channels around the edges. The main complaint I've seen on these is that they are priced like custom mats, but really aren't a custom fit. Several posters have commented that Costco has mats that fit like they were made for the Prius at only $20 or so for the set of four floor mats or the single cargo mat. I've been unable to find anything that fits that well at our local Costco, Sam's Club, or BJ's.
Here is WeatherTech's website:
http://www.weathertech.com/store/vehsea ... hoice_id=0
This dealer has many customer reviews for both the floor and cargo mats, including some by Prius owners:
http://www.autoanything.com/products/pr ... floor_mats
I expect the ExactMat will suit my needs just fine for the cargo area, but without the edge channels I'm not sure how well it will work for fishing & scuba gear. I would also like to have something that covers the split seat backs when one or both are folded down. For the floors, I'm really tempted to get Metro's all-weather mats, but I'm holding off because so far they are only offering them in black (I prefer brown or tan to match the interior).
http://www.metrotpn.com/ProductDetails. ... rtIndex=11
Hope this helps, and that others follow with better suggestions.