In my experience, the coating is where you need to concentrate your attention in regards to abrasion. Its much easier to repair the coating in most cases than frayed and worn fabric, but heavier and/or denser fabric does take longer to wear through than lighter cloth (not to mention heavier cloth gives greater puncture resistance). Rub strips do help protect high-wear areas like the keel, stems, and (sometimes) chines, the skin between keel and chines is still vulnerable; the skin will deflect, which does help to some extent. Most if not all of the proven coatings have been mention in other responses, however I do think there are other coatings that may work well on skin boats if you are in the mood to experiment.

Spray-on truck bed liner looks like a nice avenue to explore, but I think the typical qualities of the products may pose some problems. They are usually textured (not such a good thing for boat hulls, and I suspect will make matters worse if you are sliding over rocks), are engineered to be applied in very thick coats (1/4 inch, much heavier than necessary), and often require special spraying equipment to apply. A few coats of brush-on polyurethane might be necessary to get the best adhesion. Perhaps applying these materials with a squeegee would allow them to be worked into the fabric and control the texture?

Similar to the spray on bed liner products, self-vulcanizing rubber coatings look interesting. Some of the products I've seen are used in high-abrasion applications requiring a lot of flexibility, such as protective coatings for rope, foam bumpers, and molded urethane. Another materials is used in roof applications, but is advertised as a "low-cost" replacement for Hypalon. A rubber coating may be more "grabby" when trying to slide over rocks, so even if highly resistant to abrasion, they may create their own problems.

Lastly, in Mike Bielski's summer 2009 Masik article, he mentions a single-component water-based polyurea that looks promising. I purchased a gallon to try, and on paper it looks very good (just have to wait for warmer weather to use it). If it is tougher than Zar, and by all indications it should be tremendously tougher, I'll be quite happy with it. The only downside is that it may be more difficult to tint than oil-based polyurethanes, but I'm going to give it a shot anyway. :-)

: Any suggestions for the best skin/coating for a boat that will see
: a lot of abrasion? I am going to build a SOF canoe to use on
: moving water. It will most likely see a lot of abrasion
: scrubbing the bottom. I will be using rub strips, but I still
: need something tough.