Apple has released a new update for iOS. This update, 5.1.1, contains a few bug fixes, but nothing major.
Included in this update are improved HDR options for photos taken using the Lock Screen. Also, AirPlay reliability has been improved. The oft talked about issue "Unable to purchase" alert has now been solved. Lastly, Apple has improved syncing between Safari Bookmarks and Reading List between Mac OS X Lion and iOS.
Small update, can be downloaded directly from Apple by plugging your device into your computer and selecting Update or you can simply go to Settings > Software Update on your device.