Google App Engine makes it easy to build an application that runs reliably, even under heavy load and with large amounts of data. The environment includes the following features:

• dynamic web serving, with full support for common web technologies
• persistent storage with queries, sorting and transactions
• automatic scaling and load balancing
• APIs for authenticating users and sending email using Google Accounts
• a fully featured local development environment that simulates Google App Engine on your computer

Google App Engine applications are implemented using the Python programming language. The runtime environment includes the full Python language and most of the Python standard library.

Here is a video about developing and deploying an app on the Google App Engine:

Read more at http://code.google.com/appengine/