You’ve an locked iPhone 3G/3GS or you’ve accidentally locked it, and now you only see “iTunes and Data-cable” picture on your iPhone screen and when you put your SIM and plug in, iTunes says “SIM card inserted in this phone doesnot appear to be suppported”. Well you can activate iPhone by jailbreaking it, but there are times when Jailbreak tool is not available for that particular version of iOS, in that case you can use this method.
Sherif Hashim (iPhone Hacker) today posted a nice video where he showed how to activate iPhone 3G/3GS without jailbreaking. All you need SIM card like chip called Phone Book card, which according to Sherrif costs around $4-$5 only, Just Put it on your iPhone 3G/3GS instead of SIM, iTunes will automatically activate your iPhone and if its locked then atleast you can use it all its features apart from making calls.
Note: This will not unlock your iPhone, it will just activate. If you are looking for an unlock then you can use ultrasn0w which can unlock iPhone 3G/3GS with iOS 4.0.1
Here is a nice video done by Sherrif which will guide you on activating your iPhone 3G/3GS without original SIM: