App Inventor 2 is the new version of App Inventor available at http://ai2.appinventor.mit.edu.
It is fabulous: its much easier to setup (usually no downloads!) and it provides a much more elegant programming experience. The blocks editor loads
immediately (its now in the browser, not a Java app!). If you're a developer or checking out App Inventor
for future use, you should absolutely use AI2. However, AI "Classic" (beta.appinventor.mit.edu) will still be available for some months.
Learn about the key changes
As of December 3, 2013, the "Create" link on the App Inventor home page links to the new AI2 tool. But the App Inventor projects you've built with the "Classic" system are still available. Just go to http://beta.appinventor.mit.edu to use the "Classic" system and edit your projects.
At this time, there is no tool to translate AI Classic projects into AI2 projects
Even though your teaching materials will need to be changed to some degree, you should make the switch. The experience for your students will be so much better-- once you try AI2 it is hard to go back to the "Classic" version! Its also important to note that the blocks in AI2 are essentially the same, with a few minor exceptions. So you mainly need to change your tutorials/lessons that deal with mechanics, not programming. AppInventor.org and appinventor.mit.edu have been hard at work developing new materials which you can leverage. Check out the AI2 video tutorials on this site as well as the book chapters that have been translated into AI2. MIT has also translated a number of their tutorials. If I were teaching a class, I would definitely use AI2.
The setup is much smoother. If you have an Android device and a normal WiFi connection, you can generally get started within minutes without downloading anything to your computer. If you are using App Inventor in a school/organizations with firewall issues, there is support for using a USB connection and for using an emulator. Checkout these instructions
We're working hard here at appinventor.org to update the App Inventor book, all the video tutorials, and the course-in-a-box. Bear with us during this change, but please check out the following: