Man, you should look in to a side by side utility. I picked up a John Deere Gator utility that had rust from golf course use (fertilizer) for under a thousand bucks, has a dump bed and is made for the kind of stuff you do.

That sounds like a sweet deal. Anyway you could send us a photo of yours?

Just go see my latest blog post for pics!

I reckon you could rig up a simple balance crane - perhaps a tripod of saplings, lashed at the top, with another sapling for the crane arm. Then a counterweight on the non-lifting end of the arm to take most of the load of a bucket of rocks. Maybe use a bucket of water for the counterweight, so you can adjust it easily for lifting different stuff.

With it set up just right, you should be able to easily lift a bucket of rocks and swing it over onto the ATV!

Maybe its time to invest in an Atv trailer. They make some smaller ones with a plastic bed, Atv type tires, and the ability to dump. Seems like this could greatly improve your labor efficiency and save your back too.