NodeManual -- by Cloud9 IDE, a fork of the official Node.js API documentation, with a different organization, examples you can run in the browser, and additional tutorials
NodeBits -- by Tim Caswell, a site dedicated to keeping the NodeJS spirit of innovation and creativity alive. This is done by providing a constant stream of ideas and sample projects.
justjs -- by Tom Boutell. A blog featuring a series of node.js tutorials, starting with the basics of installing Node and MongoDB on your own computer and building from there into creating full-fledged node apps, beginning with the justjs.com blog itself.
Mastering Node - Open Source eBook by TJ Holowaychuk and the node community