Serial iPhone tinkerers from the iPhone Dev Team have released a new version of Greenp0ison just days after Apple blocked access to iBooks through hacked iDevices.
The Apple-imposed roadblock stopped law-abiding owners of jailbroken iPhones, iPods and iPads getting at DRM-hobbled titles they had legitimatley purchased from Apple's own iBooks Store but did nothing to prevent the installation or use of the same titles pirated from more nefarious sources.
Greenpois0n RC6.1 for iOS 4.2.1, which suppoprts all iPod Touch variants, all iPhones from the 3G upwards (including the Verizon version running 4.2.6) and Apple TV is available now for Mac and Windows right now with a Linux version expected to follow shortly.
Jailbreaking your iToy might break it and makes Steve Jobs really sad so you really shouldn't do it. Unless you realy want to.