Jesus Diaz over at Gizmodo has stated that the newest version of 3.0, version 7a341, installed and works fine on his iPhone 3G. He wrote a miniblog updating his status as he installed the 3.0 version on his phone. The 7a341 version should be downloadable on your favorite bittorrent site and can be installed without needing a developer license. Also unless there are some major changes done soon it should be the version that is released on June 17. So if you feel brave enough and don’t care if your device is jailbroken or not, then download iPhone 3.0 7a341 and give it a spin!
Note: The image is called iPhone1,2_3.0_7A341_Restore.ipsw. It should be 230.1MB
Warning: Do this at your own risk