As you may have heard in the technical press, Microsoft is a more open-source friendly place these days, and has embraced GitHub for a number of high-profile projects. As a result of this shift and an internal push to move to git generally, I've updated my existing CodePlex projects so that I can easily mirror them to GitHub. For the immediate future, I plan to maintain both sites equally with the bulk of the documentation still residing on CodePlex, but you can get full source and releases from either location thanks to the magic of distributed VCS.
In addition, all six of these projects is now licensed under MIT rather than MS-PL. The terms of both licenses are basically the same, but in legal circles the MIT license is more widely understood and is considered more 'standard'. Of course, I'm Not A Lawyer, so you should make your own determination about the change of license.
DirectX Tool Kit
Related: UVAtlas: Return of the Isochart
Sample Content Exporter
In addition to the Microsoft GitHub repositories above, I've also set up a personal GitHub project to host the Samples Content Exporter sample which has been updated to support VS 2012 with Autodesk FBX SDK 2014.1 or later, and VS 2013 with Autodesk FBX SDK 2015.1.
There is a personal GitHub project hosting the various DirectX Tool Kit SimpleSample projects.
DirectX SDK Samples
Finally, I've setup another personal GitHub project to host the cleaned up DirectX SDK samples that have been updated to not require the legacy DirectX SDK to build.
The various DirectXMath extension blog posts now have their own projects as well on GitHub: DirectXMath instruction set extensions, spherical harmonics math, and digital signal processing.
Update: There is now a DirectXMath GitHub which hosts the library as well as all related extensions.