We were in Xinjiang for 16 days in October 2012 and Ablajan was our driver and guide for the North Xinjiang leg of our tour. A Turpan native who is now based in Urumqi, Ablajan is very knowledgeable of the area. He is also personable and a safe driver.
There are only a handful of drivers in Xinjiang who hold a tourist guide license and can speak fluent Uighur, Mandarin and English. Ablajan is one of them. Engaging his services will mean you can save on engaging a separate tour guide. He is also not affiliated to any tour agencies, which means fairly transparent costs.
We highly recommend him if you're looking for a private driver rather than go through a tour agency in Xinjiang. I believe Ablajan is also able to accept South Xinjiang assignments.
Email: email@example.com or firstname.lastname@example.org