While we're still waiting on the iPhone 4S Unlocking software from the Dev Team, we have some hardware solutions available.
A few days ago we told you about intermediate, and now another has appeared. The R-SIM-Card is model of turbo-SIM card for iPhone 4S, which will unlock your phone.
So you can use it on any compatible GSM network in the world, this mean that your iPhone 4S will be Factory Unlocked . The R-SIM looks like a Gevey Sim. No need to jailbreak your iPhone or any modification on the usual SIM card.
But the device certainly has its limitations. The R-SIM not work with 3G networks. So it will be limited to the slower GPRS browsing speeds, while you are away from Wi-Fi.
R-SIM for iPhone 4S is available from Shipping for this product is free, and the following site says you can get to you within 2 weeks.