GreenPois0n has been updated to add support for jailbreaking iPod touch 2G (MC and Non-MC Model) running iOS 4.1. You can either use Windows, or the Mac version of GreenPois0n RC4 to jailbreak iPod touch 2G on iOS 4.1. Support for iPod touch 2G in Linux version of GreenPois0n will be added soon.
Instructions for jailbreaking are exactly similar to the last release. Simply follow our step by step guide posted here (for Windows), or here (for Mac) to jailbreak iPhone 4, 3GS, iPad, iPod touch 4G / 3G / 2G on iOS 4.1 with GreenPois0n.