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:
Platforms: The code is designed to build with the Windows 8.x SDK using Visual Studio 2010, 2012, or 2013 and works on Windows Vista, Windows 7, Windows 8.x Win32 desktop, Windows Store apps, Windows phone 8.1, and Xbox One.
The README.TXT in the ZIP package contains additional information, and see Shawn's posts here and here with some code snippets for usage.
Here's a handy table of equivalents for D3DX (see Living without D3DX for a complete listing):
Model, ModelMesh, ModelMeshPart
D3DXCreateBox D3DXCreateCylinder D3DXCreateSphere D3DXCreateTeapot D3DXCreateTorus
Where XXX is "DDS" for working with .DDS files, or "WIC" for working with WIC-supported bitmap image formats such as .BMP, .JPG, .PNG, etc. Note that .TGA is supported by legacy D3DX and by DirectXTex, but not by DirectXTK.
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.