boost.org

The Boost C++ Libraries are a highly respected and versatile set of C++ libraries that work well with the Standard C++ Library. They are available for use by both commercial and non-commercial users with minimal restrictions. The Boost organization supports research and education on C++ and offers free, peer-reviewed, and portable source libraries for a broad range of applications. Boost is compatible with most modern operating systems, has pre-built packages for popular Linux and Unix distributions, and welcomes participation from individuals and organizations. The libraries are distributed under the Boost Software License, Version 1.0.