C++ streams are great in theory.

libcaca

Any. “This is a implementation of N4562 std::experimental::any (merged into C++17) for C++11 compilers.”

Jyt. “Jyt is a just-in-time compiler for C++”.

Microsoft/cpprestsdk. “The C++ REST SDK is a Microsoft project for cloud-based client-server communication in native code using a modern asynchronous C++ API design. This project aims to help C++ developers connect to and interact with services.”

Curl for People. “C++ Requests is a simple wrapper around libcurl inspired by the excellent Python Requests project.”. Also see Github at: whoshuu/cpr.

Urdl. “Urdl is a cross-platform C++ library for downloading web content using a URL. It provides an easy-to-use extension to standard C++ iostreams and an asynchronous interface for use with Boost.Asio.”. Also see Github at: chriskohlhoff/urdl.

google/gumbo-parser. Gumbo is an HTML5 parsing library written in pure C99 with no outside dependencies.

lazytiger/gumbo-query. “c++ library to provide jQuery style api for gumbo library”.

pugixml. “Light-weight, simple and fast XML parser for C++ with XPath support”.

Deploying C++ documentation.

michaeljones/breathe. “ReStructuredText and Sphinx bridge to Doxygen http://breathe.readthedocs.org/”.

jessevdk/cldoc. “clang based documentation generator for C and C++”.