As you may have noticed, the source code for Android OS 2.2, which we call Froyo, has been released.

The Android OS 2.2 SDK that was released at Google I/O contained a preview of the Froyo system image and today, we are releasing an update to bring it into sync with the system image pushed to Nexus One devices.

I encourage all developers to use the SDK manager to update to this version.

Source: http://android-developers.blogspot.com/2010/07/android-22-sdk-refresh.html