DjayB6 (@DjayB6) has just released PwnageTool bundles to jailbreak  iPhone 3GS 4.3.1 (Old+New Bootrom). You can use these bundles to create iOS 4.3.1 custom IPSW for iPhone 3GS which on restore through iTunes will jailbreak your iPhone on iOS 4.3.1 with fully working Cydia. It is a tethered jailbreak which require you to use TetheredBoot Utility to put your iPhone into tethered jailbroken state on every restart.

Restoring stock iOS 4.3 IPSW to your iPhone 3GS upgrades its baseband to 05.16.01. To unlock iPhone 3GS baseband 05.16.01 with Ultrasn0w, you must upgrade it to iPad baseband 06.15.00. It is the same iPad baseband hack which can be used to unlock iPhone 3GS/3G 05.15.04 & 05.14.02 baseband.

Now you can jailbreak iOS 4.3 GM on iPhone 3GS (New Bootrom) using PwnageTool bundle. Unlike PwnageTool bundle for iPhone 3GS (Old Bootrom), it will be a tethered iPhone 3Gs jailbreak which means if you will loose power of your iPhone due to low battery or any other reason, you will have to boot into a tethered jailbroken state using Tetheredboot Utility.

DjayB6 has released his PwnageTool bundle to jailbreak iOS 4.3 GM on iPhone 3GS (Old Bootrom). DjayB6 has also updated Ramdisk Fixer to v1.5.2 which now support iPhone 3GS and fixes multiple user-accounts issue. Unlike PwnageTool bundle for iPhone 4, this bundle can jailbreak iPhone 3GS (Old Bootrom) untethered.

An iPhone hacker named Nadeem Ateyeh (@Nadeem97) has just released PwnageTool bundles for iPhone 4 and iPhone 3GS which can jailbreak iOS 4.2.1 untethered on both of the said devices without upgrading their baseband version. After jailbreaking iPhone 3Gs with PwnageTool, you will be able to unlock it with the latest version of Ultrasn0w available.

MFST.GUY has released PwnageTool bundle to jailbreak iOS 4.2 (GM) on iPhone 3GS (Old Bootrom). You can use this bundle to patch the latest version of PwnageTool (v4.1.2). Once patched, you will be able to create custom IPSW iOS 4.2 GM which on restore through iTunes will jailbreak iOS 4.2 on iPhone 3GS (Old Bootrom) without upgrading its baseband version.

iH8sn0w has released an updated version for Sn0wbreeze (v1.7) which can jailbreak iOS 4 on iPhone 3GS (New Bootrom) and iPod Touch 2G (MC models). If you have an iPod Touch 3G then either you should be on iPhone OS 3.1.2 or you need to have your SHSH blobs saved for iPhone OS 3.1.2 inorder to jailbreak iOS 4 with Sn0wbreeze v1.7.

AKi_nG has just released a video in which he jailbreaked iOS 4.0 on iPhone 3GS (NEW BOOTROM) via Sn0wbreeze (unreleased version) and iBooty 4.0. For those who don't know: Apple updated the iBoot of iPhone 3GS after 4 months of its release. Now there are two types of iPhone 3GS, one with old iBoot (359.3) and the other with new iBoot (359.3.2) version.

MSFT.guy has released PwnageTool bundles to jailbreak iPhone iPhone 3GS on iOS 4. These bundles act as a workaround to allow current PwnageTool 3.1.5(Dev-Team official) create iOS 4 custom firmware files for iPhone 3GS, as the PwnageTool averts the baseband upgrade during jailbreak, therefore we can unlock iPhone 3GS by using blacksn0w or Ultrasnow. MSFT.guy has a history of modifying official jailbreak tools to add support for latest firmwares, previously he patched blacksn0w to work...