Starting today, Nexus One users will begin to receive the Android 2.2 (codenamed Froyo) over-the-air software update on their phones. This update provides some great new features including support for making your handset a portable hotspot and support for Adobe Flash within the browser. For a complete list of everything we�ve included in Android 2.2, please see the Android 2.2 Platform Highlights.
In order to access the update, you will receive a message on your phone's notification bar. Just download the update, wait for it to install, and you should be all set. This update will be rolled out gradually to phones - and most users will receive the notification by the end of the week . We hope you enjoy these new features.
source: Nexus One | News and Updates Monday, June 28, 2010