Surprisingly enough the latest release of iOS 4.1 beta is jailbreakable using redsb0w 0.9.5 beta 5. All you need is the latest iOS 4.1 firmware for iPhone 3G or iPod touch 2G (non-MC Models) and you can jailbreak it using Redsn0w on Windows and Mac. I repeat, this is strictly for iPhone 3G and iPod touch 2G (non-MC models) only.
Instructions to jailbreak iOS 4.1 beta using Redsn0w 0.9.5b5 is exactly same to the one we followed for jailbreaking iOS 4.0. Here is a brief guide
1. Download iOS 4.1 Beta from Apple Developer Center
2. Now download redsn0w 0.9.5b5-5 [Windows | Mac]
4. Follow our step by step guide on how to jailbreak iPhone 3G with redsn0w
5. Once you have jailbroken your phone, you can unlock it using ultrasn0w 0.93 (on any baseband), guide for which is posted here.
Disclaimer: This guide is for educative purposes only. Do it at your own risk. We are not responsible for any damage that may arise.