Boost provides free peer-reviewed portable C++ source libraries. The emphasis is on libraries which work well with the C++ Standard Library, in the hopes of establishing "existing practice" for extensions and providing reference implementations so that the Boost libraries are suitable for eventual standardization. (Some of the libraries have already been included in the C++ 2011 standard and others have been proposed to the C++ Standards Committee for inclusion in future standards.)
This is a companion discussion topic for the original entry at https://copr.fedorainfracloud.org/coprs/ssabchew/boost172/