I have the exact WeatherTech mat that Tony references. It's great. I got the WeatherTech floor mats for the front seats, too. The stock gray carpet gets dirty way too fast.
My favorite accessory is the cargo cover for the back. I wanted the genuine Toyota part, but at a much lower price than the dealer, and I found it here:
http://www.oempartworld.com
I purchased the cargo cover and mud guards/flaps, both cool accessories for the RAV4 EV:
PT73142090, Cargo Cover Gray Rav4/EV: $85.02 (+ shipping)
It's black, actually, but matches the interior perfectly.
PT76942091, Mudguards without Fender Flares 4pc Black Rav4/EV: $51.23 (+ shipping)
Love them. They look cool, and really keep the sides a lot cleaner. I haven't noticed a drop in range due to lower aerodynamics... heh.
Woody