Tinythinker started a post on the official forums where to find all of the items on Kari’s Hit List which is introduced in the Thieves’ Guild DLC.
Robert J. “Jairone” Mann has produced an excellent guide that he has shared on google docs that includes screenshots and detailed descriptions.
Tip: They can be completed along with the Thieves' Guild daily quest (Quest Board).
Finding all of the items on this list will reward the player with achievement points which will also increase your rank in the Thieves’ Guild. Complete the achievements by placing the items in the display area of the Thieves’ Den in Abah’s Landing.
Tip: These items are stolen items and if you are captured or killed by a guard, you will lose any of these items in your inventory. Keep some Counterfeit Pardon Edicts on hand for the more trickier items.
Below you will find a summary that will lead you to the general locations (eg. building) but doesn’t take away all of the exploration fun trying locate each of the items within each structure.