Could always ask the landowner if he'd like some trees cleared. I'm from the Allegheny Nat'l Forest region, where taking fallen dead wood that's on the ground is encouraged. Also look for "free pallets" if you're not picky about the type of wood.
I don't know where you live, but you could check the bulletin boards of any local grocery store, hardware store, or other businesses or community buildings. Some of these businesses will probably have advertisements from people in the community that have firewood.
You might also ask your friends and coworkers if they know of any. You may have a hard time finding FREE firewood, but there's bound to be some people selling it.