For me the main source of cash has always been looting dead bodies for whatever they are worth, never found anything else more profitable.I always take one handed weapons off them and armor especially.But its kinda annoying to see naked corpses everywhere, so anything more profitable then this method?

I work in mines and make fine jewelry for all of skyrims nobility.

Treasure chests in ruins. Also, anything I find that has decent value I sell to make some coin

I'm guessing the majority of mine is probably from selling the many treasures I find on an adventure. Ever find a Daedric Battle Axe of Fire for over 3000 coin? Makes you drool like a dog. After that, it's the coin I pick up randomly. The ground, chest, corpses, etc. These days do, I usually create high leveled potions for some coin and to increase my Alchemy skill.

Transmuting iron and silver into gold, making jewelery out of said gold, dungeon diving, stealing. That kind of stuff.

Grind potions like mad!

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.

Sell stuff.

Selling enchanted daggers. Now I get my gold treasure hunting.

I go to Windhelm docks, round up some lizards and sell em.

Nah seriously. i'm a thief. thats how i get most of my money. when im not stealing, i raid bandit camps, forsworn, etc all have stuff that you can sell. also sometimes i do quests because of the reward, not because i like them.

Selling Gems, Scrolls, and Potions. Staffs and Jewelry also have fairly high value to wieght ratio.

I will collect Firewood and Vegetables to sell them early in the Game, Farmers do not mind the Cabbages being slightly withered. Game (Meat gathered by hunting) can also be sold, and collecting Game is free training.