Depends on the character. Granted most of mine have made their money mostly from dungeon diving & bandit raids, but there have been at least 4 who also supplemented their income by chopping wood, especially when they're new to the world of Skyrim.
Chopping wood sounds mundane, but it actually earns quite a lot of money. I usually change the channel or surf the 'net while they're working. The wood-chopping animation lasts 30 or 40 seconds (thereabouts) which means every minute or so, I'll change the channel and aim for the wood stump again. Or sometimes I won't even change the channel. I'll just keep pressing the activate joystick while randomly 'aiming' for the stump. Sometimes, my character is making money and I'm not even in the game!
There was a thread somewhere in which somebody bought a house this way. He or she spent several hours in real-time just chopping wood (while reading a book or whatever) and wound up with all this money.