Jailbreakers rejoice! PwnageTool 4.2 to the rescue!
This Jailbreak is a tethered jailbreak meaning that you will need to connect your device to your computer each time your device requires a restart. The Jailbreak is in its early stages and may not be entirely stable.
If you’re in a hurry to Jailbreak so that you can start using iOS4.3.1 then run over to Redmond Pie for this walkthrough.
(Via Cult of Mac)