Note: There's a new Google Apps Marketplace experience! Beginning November 19, 2013, new listings may only be created using the new version: existing developers may need to create a new Chrome Web Store account to publish new listings. Refer to the new documentation for more information.
This document provides some suggestions on how to build an application developed for the Google Apps Marketplace or an in-house application using the Google Apps extensions console. Google won't be able to write your application for you, but the following are some pointers that might make development easier.
Google Apps Users
Google Apps is used by over 4 million businesses and universities — organizations that understand the benefits of working and collaborating in the cloud. The best Google Apps Marketplace applications will play to the strengths of the cloud — offering quick, always-available access to data, collaboration abilities, and deep integration with the Google Apps suite.
Google provides a wealth of APIs to aid you in the various stages of application development. Use of these APIs is completely optional, but may make your development easier.
Google Web Toolkit (GWT) is a development toolkit for building and optimizing complex browser-based applications. GWT is used by many products at Google, including Google Wave and Google AdWords. It's open source, completely free, and used by thousands of developers around the world.
Google Apps Marketplace developers are free to deploy their applications on a server stack of their choosing. Developers looking for options for their deployment environment should make sure to check out Google App Engine. Google App Engine offers both Java and Python runtimes.