Cinder is free to download, open-source and available for Mac OS X and Windows. The latest version is v. 0.8.5, released on April 24, 2013.
To keep up-to-date with Cinder's development, consider working from the github repository directly.
This guide walks you through getting setup with Cinder and Github.
To get started, check out the Welcome.html file included in the download.
And if you haven't read it yet, Robert Hodgin's Hello, Cinder tutorial is a great way to get a guided tour of Cinder.