Download it here: Kinect for Windows SDK v1.8.
Also: Kinect for Windows Developer Toolkit v1.8.
Here’s Bob Heddle with the announcement:
I am pleased to announce that we released the Kinect for Windows software development kit (SDK) 1.8 today. This is the fourth update to the SDK since we first released it commercially one and a half years ago. Since then, we’ve seen numerous companies using Kinect for Windows worldwide, and more than 700,000 downloads of our SDK. […]
Kinect for Windows SDK 1.8 includes some key features and samples that the community has been asking for, including:
Updated SDK, with HTML5, Kinect Fusion improvements, and more