The Atom Shell framework lets you write cross-platform desktop applications using JavaScript, HTML and CSS. It is based on node.js and Chromium and is used in the Atom editor.
Prebuilt binaries of atom-shell for Linux, Windows and Mac can be found on the releases page.
Guides and the API reference are located in the docs directory. It also contains documents describing how to build and contribute to atom-shell.
There is an atom-shell category on the Atom forums
as well as an #atom-shell channel on Freenode.