MSVC's implementation of the C++ Standard Library.

Sol3 (sol2 v3.0) - a C++ <-> Lua API wrapper with advanced features and top notch performance - is here, and it's great! Documentation:

The C++ Core Guidelines are a set of tried-and-true guidelines, rules, and best practices about coding in C++

Toolkit for creating Metro styled WPF apps

A framework that allows developers to cobble together a better UI for their own WPF applications with minimal effort.