Ladies and gentlemen the iPhone OS 3.1 Software Update is now available for the iPhone, iPhone 3G and iPhone 3GS.  Simply hop on over to Apple’s website and download the latest version of iTunes (iTunes 9) and connect your iPhone to your computer to begin the installation process.  The servers are under quite a bit of strain right now so it might take you a while (currently downloading at 150KB/sec on a 18Megabit connection myself).  For a full list of the improvements and features in the 3.1 OS Software update you can refer to Apple’s documentation below:

This update contains bug fixes and improvements, including the following:

• Genius recommendations for Applications
• iTunes 9 support
• Genius Mixes
• Organize your apps directly in iTunes
• Improved syncing options for music, movies, TV shows, podcasts and photos
• iTunes U content organization
• Redeem iTunes Gift cards, codes and certificates in the App Store
• Display available iTunes account credits in the App Store and iTunes Store
• Browse and download ringtones wirelessly from the  iTunes Store*
• Save video from Mail and MMS into Camera Roll
• Option to “Save as new clip” when trimming a video on

Improvements for the iPhone 3GS

• Better iPhone 3G Wi-Fi performance when Bluetooth is turned on
• Remotely lock iPhone with a passcode via MobileMe
• Use Voice Control on iPhone 3GS with Bluetooth headsets
• Paste phone numbers into the Keypad
• Option to use Home button to turn on Accessibility features on iPhone 3GS
• Warn when visiting fraudulent websites in Safari (anti-phishing)
• Improved Exchange calendar syncing and invitation handling
• Fixes issue that caused some app icons to display incorrectly

Products compatible with this software update:

• iPhone
• iPhone 3G
• iPhone 3GS