Jailbreak Iphone 3G framware 3.1.3 baseband 5.12.01
 

1- download redsn0w 0.9.3 beta http://www.mediafire.com/?gc3dzmnv3v3
2- download the 3.1.2 for 3G firmware , i repeat 3.1.2 for 3G, http://www.poorlad.com/iCommunity/ and save on ur desktop
3- attach the iphone to ur laptop
4- run redsn0w
5- browse to 3.1.2 that u downloaded
7- choose install cydia only
8- when u r instructed, turn ur phone off
9- follow the instructions

it worked for me test it today :)