Apple has released iOS 5.1 and is available for a download for iPhone 4S, iPhone 4, iPhone 3GS, iPod Touch 4G, iPod Touch 3G, iPad 1 and iPad 2.
Release Note of iOS 5.1
Japanese language support for Siri (availability may be limited during initial rollout)
Photos can now be deleted from Photo Stream
Camera shortcut now always visible on Lock Screen for iPhone 4S, iPhone 4, iPhone 3GS and iPod touch (4th generation)
Camera face detection now highlights all detected faces
Redesigned Camera app for iPad
Genius Mixes and Genius playlists for iTunes Match subscribers
Audio for TV shows and movies on iPad optimized to sound louder and clearer
Podcast controls for playback speed and a 30 second rewind for iPad
Updated AT&T network indicator
Addresses bugs affecting battery life
Fixes an issue that occasionally caused audio to drop for outgoing calls
Download Links For iOS 5.1 IPSW
iPad 2 (AT&T)
iPad 2 (Verizon)
Jailbreakers should avoid updating to iOS 5.1.