iPhone 3G
firmware version 4.0.0 can be found here: iPhone1,2_4.0_8A293_Restore.ipsw
iPhone 3G 4.0.1: iPhone1,2_4.0.1_8A306_Restore.ipsw
iPhone 3G 4.0.2: iPhone1,2_4.0.2_8A400_Restore.ipsw
iPhone 3G 4.1.0: iPhone1,2_4.1_8B117_Restore.ipsw
iPhone 3G 4.2.1: iPhone1,2_4.2.1_8C148_Restore.ipsw
iPhone 3G 4.0.1: iPhone1,2_4.0.1_8A306_Restore.ipsw
iPhone 3G 4.0.2: iPhone1,2_4.0.2_8A400_Restore.ipsw
iPhone 3G 4.1.0: iPhone1,2_4.1_8B117_Restore.ipsw
iPhone 3G 4.2.1: iPhone1,2_4.2.1_8C148_Restore.ipsw