Sn0wbreeze 2.0 is out! Just like PwnageTool for Mac, you can now cook custom firmwares of iOS 4.1 on Windows without upgrading the baseband, which ultimately means that you can use ultrasn0w unlock software to unlock your phone on the older baseband.
Sn0wbreeze 1.7 for 4.0 (for Windows) has been released. This release supports iPhone 3GS (old and new bootrom), iPhone 3GS, iPod touch 2G (MC and non-MC models), and iPod touch 3G. Though iPhone 3GS (new bootrom), iPod touch 2G (MC models) and iPod touch 3G will have to be either on 3.1.2 firmware, or will need to have their SHSH blobs saved for iOS 3.1.2 in order to successfully jailbreak these devices on iOS 4. Also the jailbreak for iPhone 3GS (new bootrom), iPod touch 2G (MC models) and iPod touch 3G on iOS 4 will be tethered, which means whenever you turn off your phone, you will need to re-connect it to a computer to be able to turn it back on.