The Android 2.1 SDK is now finally available, being the first official SDK to actually be released after the availability of a phone running it (the Nexus One). Note to users: "Android 2.1 does not add significant user features, see the Android 2.0 Platform Highlights document for the latest user features."
As expected, the SDK adds support for active dynamic wallpaper development and a much visually-stunning 3D-enabled Gallery app. Furthermore, there are changes to signal strength visual output, view selectors for applications and updates to the WebKit rendering engine to allow for geolocation support. New settings are also included for app cache, web storage, zooming based on screen density and methods for handling video, browsing history and custom Views along with app cache limits.
No unexpected huge changes here, but it does indicate that 2.1 will be indeed coming to other Android phones like the Motorola Droid and other HTC smartphones.