Apple released the iPhone 3.0 firmware and also the iPhone 3G S which comes with the latest firmware, but the old iPhone 3G phones once upgraded with the new firmware would lose the network if it was an unlocked phone earlier. And the dev team has released the first tool to unlock the 3.0 firmware – Pwnagetool 3.0 which is helpful to jailbreak phones with latest firmware and also unlock for any network. The tool is available only for mac users, as of now and the same for windows would be available soon.
With Pwnagetool, you can unlock the Original iPhone (1st Generation), Original iPod touch (1st Generation) and the iPhone 3G. But this tool would not work to unlock the iPhone 3G S which is just released into the market. Soon, Dev team would also release the ultrasn0w which would be the ultimate tool to unlock the latest firmware iPhone version. Here are a few mirror links to download Pwnagetool to unlock the iPhone 3.0 firmware -