ICEcoder is an open-source 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.
Because it can be web based you can use it from any internet enabled computer with a modern browser and because it's open-source, customise it to your liking, integrating with online services. If you'd like to use it as a desktop code editor, no problems, you only need PHP 5.0+ (though 5.3+ is recommeded), so you can use on Linux and on PC via MAMP or XAMPP and Mac via WAMP (or another PHP installation).
ICEcoder was created because web devs (like myself) always complained their code editor didn't do exactly what they like. They're often bloated with features, slow and awkward. Conversely, ICEcoder is lightweight (under 1.2mb including all plugins) and boots in seconds (often 1-2s). Oh, and it's also free (and always will be!). Enjoy!