Seas0nPass has been updated to support an untethered jailbreak on iOS 4.4.4 the latest version of the Apple TV OS. You can get the tool from Seas0nPass.com.  
Details from Firecore:

Happy New Year! Today we are happy to release an updated version of Seas0nPass that supports an untethered jailbreak of the latest 4.4.4 (iOS 5.0.1) AppleTV software. Big thanks goes to the world famous@pod2g for doing the lion’s share of the work to make this new version possible.

What’s new in AppleTV 4.4.4?

 
 

• AirPlay Mirroring: Now with video mirroring – wirelessly stream what’s on your iPad 2 screen to your HDTV.
• Photo Stream: View photos recently taken on your iOS device and pushed to your Photo Stream in iCloud.
• Trailers: A whole new way to browse and view hundreds of the latest theatrical trailers.
• National Hockey League: Watch live games. View highlights, scores, and more.
• Wall Street Journal Live: Watch up-to-date news, business commentary, and financial analysis from leading experts.
• Audio output: Addresses an issue in which audio may not play through the optical port when the TV is turned off.
• Netflix: Added support for Netflix in Mexico and Latin America.
• Stability and performance: version 4.4.4 includes general performance and stability improvements, including a fix for an issue that displayed an error when playing some video content.

 
 

Note: If you’re already running a tethered version of 4.4.4 you will need to re-jailbreak using Seas0nPass to take advantage of the new untethered version.

 
 

Which plugins are supported on 4.4.4?

 

• Couch Surfer (works)
• Last.fm (works)
• Media Player (works)
• NitoTV (works)
• Overflow (works)
• Remote HD (works)
• Rowmote (works)
• RSS Feeds (works)
• Weather (works)
• XBMC (works)
• Plex (not working)