When the iPhone 4S was launched here in the UK you could either purchase it on a contract from one of the mobile providers, or you could purchase an unlocked version direct from Apple.
With the US launch of the iPhone 4S, it was only available to purchase from one of the US carriers, which included Sprint, AT&T and Verizon, and now Apple is selling an unlocked version of the iPhone 4S in the US.
You can now purchase an unlocked iPhone 4S direct from Apple online or at one of the Apple stores, and the 16GB iPhone 4S retails for $649, the 32GB iPhone 4S retails for $749 and the 64GB iPhone 4S retails for $849, you can find out more details over at Apple.
Source Engadget
Have a look at our handy guide on the difference between the iPhone 4 and iPhone 4S. and also our article on the difference between the iPhone 4S and iPhone 5 to see all about the new iPhone 5.