You have today a lot of options. Here are just a few:
- Cloud9, an IDE for JavaScript, Python, PHP, and Ruby. Cloud9 uses the HTML5 FileSystem capability and AppCache to sync files, so you can even code offline.
- Neutron Drive seems like a good option with a close integration with Google drive and lots of languages its support.
- ShiftEdit - which give you many options to develop in your language: PHP, Ruby, HTML, CSS and JavaScript and then by using (S)FTP you can save your work to Dropbox or Google Drive.
- Kodingen is another IDE that includs: Code Editor, Cloud Hosting, Database Administration and collaboration
- Codey - Easy to use code editor for HTML, PHP, CSS, JS.
- Akshell - Server-side JavaScript development and hosting platform. They got some git integration built in their IDE.
- eXo Cloud IDE - an IDE that support: HTML/CSS/JS and PHP/JAVA/RUBY and many more options.
For more, here is an 'old' post I wrote on this topic when the first Chromebook was launched.