Aaron from Columbia on 9/6/2010 9:59:20 PM:
On my mountain bike, I ride Kenda Klimax Lite 26x1.95" tires (although, they're more like 1.7"). Very little tread and extremely light.
I've ridden at least a couple hundred miles on my road bike, with 25c slicks at 80psi, too, and they get the job done just fine. A typical rider will probably prefer something like a 28-38C tire on a road or cyclo-cross bike, just to help smooth out the rocks.