The latest AT&T device to receive an upgrade to Jelly Bean is the Samsung Galaxy Express, which should see Android 4.1 begin pushing to handsets today. The update comes with such Google standards as actionable, rich notifications, Google Now, and Face Unlock, while Samsung has made additions of their own such as Easy Mode and Blocking Mode.
The full details of the update can be found at the AT&T blog post linked below. To see if the new software is available for your device, navigate to Applications > Settings > About Device > Software Update > Check for Updates.
[via AT&T]