We're running low on firewood this year, but I've got a bunch of pallets, so I started cutting them up. Not really recycling, I know, but man does that wood burn HOT! Mostly red oak, some fir. I just took the slats and left the stringers with all the nails. Four cuts next to the stringers on each surface of the pallet with a circular saw does the trick. Using a blade you don't care too much about is recommended.
I got 200+ pounds of firewood out of 10 pallets for about an hour's work, and I have 20 more on hand to harvest. My supply is unlimited - our local Agway always has them on hand for the asking.