Google has made the full 4.1 Android SDK available for download, along with a revised set of SDK tools (20.1.1) and the NDK (rev 8b). As always, the SDK and assorted tools are available for Windows, Mac and Linux, and are a must have for any serious Android application development. You can grab the updates through the SDK manager of your existing installation, or at the Android Developers site.
Speaking of serious application development, Android engineer Nick Butcher has also written a great blog post about writing apps that take advantage of the new Jelly Bean API and the features found on the Nexus 7. He brings up a great point -- for most users, the Nexus 7 will be their first look at Jelly Bean. You want your applications to shine, and not just work. He gives tips and methods so that your apps can do just that. Be sure to give it a read at the source link below.
Source: Android Developers blog