The new "Absinthe A5" jailbreak comes via pod2G and the Chronic Dev Team, which teamed to release an enhancement to the popular Greenpois0n jailbreaking tool. Sadly for Windows and Linux users, the best we can say for them is ... "soon, soon."
The tool has only been released for Mac OS X as of now, but versions for Windows and Linux are scheduled to follow quickly.
There's even bad news for those with Macs. Due to the announcement and the (one might imagine) sudden popularity of the Greenpois0n site, the site is experiencing intermittent connectivity issues (translation: it's down a lot).
Absinthe will jailbreak the iPhone 4S running iOS 5.0 (9A334) and 5.0.1 (9A405 and 9A406) and all models (wi-fi, CDMA, GSM) of the iPad 2 running iOS 5.0.1 (9A405).