Apple has released iPhone OS 2.2 and iPhone OS 2.2 for iPod touch Software Update which contains many bug fixes and improvements including:
• Enhancements to Maps
– Google Street View
– public transit and walking directions
– display address of dropped pins
– share location via email
• Enhancements to Mail
– resolved isolated issues with scheduled fetching of email
– improved formatting of wide email messages
• Improved stability and performance of Safari
• Podcasts are now available for download in iTunes application (over Wi-Fi and cellular network)
• Decrease in call set-up failures and call drops
• Improved sound quality of visual voicemail messages
• Pressing the Home button from any Home screen takes you to the first Home screen
• Preference to turn on/off auto-correction in Keyboard Settings
Update your iPhone or iPhone 3G or iPod touch via iTunes Update:
Step 1. Make sure you are using iTunes 8. Connect your iPhone to your computer.
Step 2. When iTunes opens, select your iPhone under Devices in the Source List on the left.
Step 3. In the iPhone Summary pane, click Check for Update.
Step 4. Click Download and Install. Do not disconnect your iPhone until the update has finished.
Step 5. There is no Step 5. Enjoy!
More info about the security content of iPhone OS 2.2 and iPhone OS for iPod touch 2.2 here.