Apple’s XML files unveiled the URL to the iPhone 2.0 Firmware. It is available for download here. The latest iPhone 2.0 firmware is build 5A345, the one shown in the XML file is build 5A347. I would recommend people to wait until Apple officially post an announcement about the 2.0 firmware release, but those who are dare devil at heart and won’t mind bricking their first generation iPhone might try to leap ahead.
You will need to install the firmware manually using iTunes by holding the Option key when clicking the “Check for Update” button in iTunes, and then a file selection box will appear for you to select the firmware file.
Again, proceed with cautions; we are not responsible for you bricking your iPhone. Many people on Macrumors forum has reported to successfully installed this firmware.