The DirectXTex library does an excellent job of providing all the 'texture content processing' functionality from the venerable D3DX library (see "Where is the DirectX SDK?"), and DirectXMath (or the older XNAMath) takes over for D3DXMath. Shawn Hargreaves and I have been putting together another utility library, dubbed "DirectX Tool Kit" or "DirectXTK", to address some additional runtime needs for Direct3D 11 applications.
DirectXTK includes the following components:
This library can be used for Windows 8/Windows 7/Windows Vista Direct3D 11 Win32 desktop applications as well as Windows Store apps (a.k.a. Metro style apps).
The code requires either Visual Studio 2012 or VS2010 with the new Windows SDK as it makes use of DirectXMath and the new SAL2 annotations.
The README.TXT in the ZIP package contains additional information, and see Shawn's posts here and here with some code snippets for usage.
Update: DirectXTK is now hosted on Codeplex. The latest version of the library, documentation, notes on future work, release history, and other information is now available there. The library now includes PrimitiveBatch and Model as well.
Windows phone 8: DirectXTK supports Windows phone 8 apps using the Windows phone SDK 8.0. See ShawnHar's post.