Today marks the public launch of Brackets, an open source, light-weight code editor built entirely with web standards. Brackets has been in "stealth mode" for a little while now. The complete source (as well as links for downloads) can be found at the Github repo: https://github.com/adobe/brackets
Brackets is not yet ready for prime time. Don't uninstall your primary editor just yet. But do kick the tires a bit and see what you think. Brackets has some very cool things going for it already, including inline editing and live connections with Chrome. It also has an Extension API that allows for adding your own features to the editor. So for example, I was able to create extensions for JSHint, CSSLint, and W3CValidation support. All using HTML, CSS, and JavaScript. (The Brackets wiki has a nice list of extensions already!)
For more, see the new Brackets blog and watch the nifty video below:
You can find more videos on their YouTube channel and be sure to follow @brackets.