This mod adds a number of handwritten notes into the game which give clues about how to find each of the Stones of 
Barenziah.  The idea for this was suggested by Jaberkaty on the official forums who wanted a more immersive method of 
searching for each stone and one that unfolds as you progress along the Thieves Guild quest path.

It's a reasonable gold sink as well, for the many players (myself included) who grumble about the abundance of gold in the game.
I've edited only vanilla assets.  Only one stone was moved (refer to the readme for details).  You shouldn't need to start a new game to use this mod but obviously if you've already finished the No Stone Unturned quest, there's no point installing this mod until your next playthrough.

It's possible for some of the holders of the notes to be killed and therefore those notes could be lost in your game.  If that 
happens and you don't know where a few of the stones are, you could download a mod which adds questmarkers to the game for 
the No Stone Unturned quest and turn on the markers. Here's one: http://www.nexusmods.com/skyrim/mods/9385/?

UPDATE:

Prowler's Profit - Non quest compatibility V1.1 (NOTE UPDATE)

I have uploaded an additional .esp that is compatible with Non quest locations for Stones of Barenziah by Globox68 which changes the locations of the quest-locked stones.
 
It won't be compatible with any quest markers mod, however as some stones have been moved.  There is a separate readme for this mod in the mod archive - ie it's not the one showing under the nexus readme tab above.

Both .esps have been cleaned with TESVEdit.