On Monday the project, which succeeds MeeGo and has already become quite controversial, released a source code preview and SDK. This HTML5-focused Linux distribution is leveraging the Enlightenment Foundation Libraries (EFL) as part of this platform too.
The Tizen source preview has the OS code, middle-ware, a basic UI, and menu interface. The SDK preview offers up the initial APIs, a web IDE, emulator, tool-chain, and documentation. At least it's now not vaporware.
Tizen also now has a few mailing lists and IRC channel.
Details on this first drop of Tizen can be found at Tizen.org.