Sell stolen items without joining the Thieves guild
Have a skill level of Journeyman in Mercantile and go to the Inn of Ill Omen. Talk to the proprietor and sell any stolen goods you have. He is the only normal merchant in the game that will purchase stolen goods. Also, invest in his shop so that he can buy more expensive stolen items.
Have two of the same items (for example, two fine steel longswords all with the same stats and health) and drop both of them. The game will not recognize them as stolen.
If you enchant a stolen item, the game no longer recognizes the item as stolen.