Sn0wbreeze 3.1.3 has been released which can jailbreak iPhone 2G, 3G and iPhone 3GS on the latest iPhone 3.1.3 firmware. One thing which is to be noted here is that it will work with iPhone 3GS only if it has the older bootrom (non-MC model). iPhone 3GS users who have upgraded to the stock 3.1.3 are still out of luck.
After releasing an update to iTunes (version 9.0.3) yesterday, Apple today has announced the new iPhone 3.1.3 Firmware for iPhone 2G, iPhone 3G, iPhone 3GS and iPod touch. One thing which is to be noted here is that this isn't the same version which runs on the newly release Apple iPad (OS 3.2). If you currently rely on your unlock for iPhone 3G and 3GS, we highly recommend you not to upgrade to this new iPhone OS 3.1.3 unless and until new tools are made available from the likes of George Hotz and the infamous iPhone DevTeam. Upgrading to iPhone OS 3.1.3 now may result in your device getting potentially locked forever.