Codio!

Cloud9 is a code editor and development environment built with browser technology yet with the power of a desktop IDE. It's available both as an online service and as a locally hosted platform.

ideone.com is a... pastebin. But a pastebin like no other on the Internet. More accurate expression would be "online mini IDE and debugging tool".

Codeanywhere is a code editor in a browser with a powerful ftp client integrated, and all popular web formats are supported (HTML, PHP, JavaScript, CSS, and XML).

Codiad is an open source, web-based, cloud IDE and code editor with minimal footprint and requirements

Koding is a developer community and cloud development environment where developers come together and code in the browser – with a real development server to run their code. Developers can work, collaborate, write and run apps without jumping through hoops and spending unnecessary money. The Cloud Development Environment

ICEcoder is a browser code editor which provides a modern approach to building websites. By allowing you to code directly within the web browser, online or offline, it means you only need one program (your browser) to develop sites, plus can test on actual web servers. After development, you can also maintain the website easily, all of which make for speedy and smart development.

ShiftEdit is a free web based IDE.Features: Syntax highlighting, Integrated (S)FTP, Tabs, Find/Replace, Revision history, bookmarks.

Powerful, Collaborative Online/Offline web IDE

Codenvy let's developers contribute to a project in seconds without installing software. Modify, run and debug code in the cloud or on-prem with no software to install.

sourceLair is a cloud based software development environment aiming to revolutionize its market by letting developers work everywhere, with the most reliable, efficient and elegant development environment available.

A Textmate like lightweight programmer's text editor right inside of Chrome. It saves files directly to Dropbox, so if you have the Dropbox sync software installed, the changes will appear locally as if you did so with a text editor! Changes will be stored remotely so naturally this same extension will pull up the same copy of the file everywhere!

CodeTasty is a programming platform for developers in the cloud. Enabling them to collaborate with others and offers features like code complete (js and php parsing), live preview, multiple layouts, revisions, terminal, dark/light theme.

Neutron IDE is a web based IDE. Neutron IDE allows you to edit code via your web browser on any server you own.

NeptunIDE is a full featured, cloud based IDE for PHP. It has dedicated CakePHP support including CakePHP autocompletion, graphical interface for bake, WYSIWYG view editor, easy creation of new CakePHP projects and much more! With NeptunIDE you can develop your applications on any PC as well as on an Android or iOS based tablet or Google Chromebook without any problems. As NeptunIDE is designed to support also touch and small resolution screens, your developing experience will be as good as on your PC. »