Apple has released iOS 5.1.1 firmware for iPhone, iPad and iPod Touch.The new firmware comes with bugs fixes.
iOS 5.1.1 has support for iPhone 4S/4/3GS, iPad 3/2/1 and iPod Touch 4G/3G.
Changelog of iOS 5.1.1
-Improves reliability of using HDR option for photos taken using the Lock Screen shortcut
- Addresses bugs that could prevent the new iPad from switching between 2G and 3G networks
- Fixes bugs that affected AirPlay video playback in some circumstances
- Improved reliability for syncing Safari bookmarks and Reading List
- Fixes an issue where ‘Unable to purchase’ alert could be displayed after successful purchase

Direct download links for iOS 5.1.1 firmware
Jailbreakers should stay away from updating to iOS 5.1.1.