After finding a lot of frustration in attempting to hunt Turtles around level 40 around Theramore I decided to wait until I was high enough to hunt Surf Gliders (found here http://thottbot.com/?m=18467) in Tanaris.

The Good:

These turtles drop speckled shell fragments (worth 9S each) almost every time. If you have skinning, they also drop the Turtle Scales needed for the Wild Leather quests at an incredible frequency along with Thick and Rugged Leather. The turtles are also well spaced out so you will never be aggro'd by more than one. They also spawn back faster than the turtles around Theramore and there are plenty more of them in a closer proximity. Also, I have never once seen anybody else hunting these turtles in my few days of farming them (your mileage on the last point may vary)

The Bad:

Intermingling with the Turtles are some nasty Giants (Coast Striders and Deep Dwellers 48-50 Elite). Avoid the coast as the Coast Striders will grab you, and avoid going too deep or the Deep Dwellers will smack you around. However, if you're smart and stay off shore, you should not be bothered. In all my time there I only got aggro'd by a giant once.

The Reward:

I hunted last night for 3 hours and my haul included:

3 Green Items (I'm looking at about 10G on the AH)
110 Speckled Shell Fragments (Sold to the vendor for ~9G 90S)
140 Turtle Scales (At the AH on my server there are never any scales up for auction and I've routinely been getting 4G 50S per 20)
~100 Thick Leather
25 Rugged Leather.

So after sales I'm esitmating my haul for 3 hours work to be in the neighbourhood of 51G, a ton of leather and some great XP. Your mileage may vary depending on your skills and server, but at the very minimum without skinning you can be looking at a good 10G+Items