Smart folks over at XDADevelopers have managed to find the unlock codes of Galaxy S devices. This means users using a locked Galaxy S (be it AT&T’s Captivate, T-Mobile’s Vibrant or even the standard Galaxy S I9000) can be unlocked to work with any other network by using simple tools.
The forum poster claims that the tool works with European Galaxy S and Engadget has confirmed to make it work with a T-Mobile SIM in Captivate and AT&T in Vibrant.
The tool works for both Mac and Windows, which you can find here along with full set of instructions.
PS: This tool does not require users to root their device and they can even lock their devices again with the extracted code.