The Codeplex site has the latest release packages, source code revision history with a Team Foundation Server source depot, documentation wiki, and issues tracker.
The official Windows SDK Sample version of DirectXTex is available on MSDN Code Gallery. The Windows SDK Sample version uses SAL2, DirectXMath, and requires the DXGI 1.2 headers to build. The Codeplex version uses SAL, can use XNAMath or DirectXMath, and optionally uses DXGI 1.2.
Update: Both are also now available on GitHub and CodePlex has been shut down.