The Chronic Dev-Team has released a minor update to Greenpois0n that brings a fix for iBooks and the Apple TV 2G Wi-Fi bug, according to OPK.
updated #greenpois0n builds for win and mac (RC6.1) are now live, these include the ibooks fix
a fix for the atv2 wifi bug has been made
You can download the latest release from here. It can be run on top of earlier builds.
To jailbreak follow one of these tutorials: