Ajax.org is today introducing Cloud9 IDE, a fresh cloud-based development platform for JavaScript incorporating HTML5, and supporting Python, Ruby and PHP.

The environment aims to enables developers to easily build, test, debug, and deploy Web and mobile applications with a minimum of technical skills and time required.

If the name of the project (repository: Cloud9 IDE) rings a bell, you may remember that it merged with Mozilla Skywriter, a Web-based framework for code editing, back in January 2011. Find out more here.

Ajax.org CEO Ruben Daniels posits that over 75 percent of websites today use third-party JavaScript widgets, and that the market for mobile apps is exploding, which means Cloud9 IDE could become a popular gateway to the cloud for a growing number of Web and mobile developers. A – wait for it – app store for Cloud9 creations is set to open later this year.

Update: also check out ShiftEdit.