If you haven’t heard of or tried Cloud IDE yet, it’s a very fine IDE in a browser developed by eXo. While not on-par with your typical Eclipse/NetBeans/IntelliJ desktop solution it goes a long way offering multiple language support, code completion, syntax highlighting and integrated javadocs.
All of this goodness now integrates with AppEngine, both Java and Python. This means that you can start from Cloud IDE, seamlessly integrate with the AppEngine management tools to create the application, debug “locally” using the eXo infrastructure, and ship it to AppEngine. Here’s a short and sweet demo of this at work, all without ever leaving the browser:
Documentation for all of this is here.
Try it out for yourself!