Here is a video of an untethered jailbreak available on the Web.

A new team called TheiPhoneDevTeam (?!?) said that they will release soon a tool which will permit to jailbreak all models of iDevice with FW 3.1.3 as the latest iPhone 3GS and iPod Touch 3G !
It seems that the release should be planned on April 12th, but WARNING it could be just a buzz...