What languages are supported by Google App Engine?

What languages are supported by Google App Engine?

Currently, Google App Engine allows you to write your applications with Python 2.5. For security reasons, some Python modules written in C are disabled in our system. Also, since Google App Engine doesn't support writing to disk, some libraries that support this and other functionalities are only partially enabled. Our developer documentation gives a good overview of the Python runtime environment. A description and full reference of Python libraries that are disabled or partially disabled can be found here.

Additionally, your website templates can include Javascript along with your HTML. Among other things, this allows you to write webservices that make use of Ajax web development techniques.

From the Google FAQ