NOTE: Those of you who rely on a carrier unlock MUST STAY AWAY from Redsn0w and stock iOS 4.3.1 firmware. Instead, use PwnageTool (on Mac) or Sn0wbreeze (on Windows).

Jailbreak iOS 4.3.1 Using Sn0wbreeze 2.5 (iPhone 3GS/4 iPod Touch 3G/4G and iPad 1 AppleTV 2G)

How to jailbreak AppleTV 2G iOS 4.3.1 (Build 4.2.1) untethered with Seas0nPass (Windows)

Untethered iOS 4.3.1 Jailbreak Using Pwnage Tool 4.3 Mac Only