...one of the most highly regarded and expertly designed C++ library projects in the world.
Herb Sutter and Andrei Alexandrescu, C++ Coding Standards
from the site ...
The Boost web site provides free peer-reviewed portable C++ source libraries. The emphasis is on libraries which work well with the C++ Standard Library. The libraries are intended to be widely useful, and are in regular use by thousands of programmers across a broad spectrum of applications.
A further goal is to establish "existing practice" and provide reference implementations so that Boost libraries are suitable for eventual standardization. Ten Boost libraries will be included in The Cpp Standards Committee's upcoming C++ Standard Library Technical Report One as a step toward becoming part of a future C++ Standard.
Although Boost was begun by members of The Cpp Standards Committee Library Working Group, participation has expanded...
Boost has its own Wiki Web: www.crystalclearsoftware.com 
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Many of the libraries are Header Only Cee Plus Plus Packages.
The Boost Libraries are maintained using Git Version Control with a set of submodules, one for each library and tool. See also Git Work Flow.
Versions
Boost is not static and all the time new libraries are being added to it. An open peer review process is used to assess each addition. Also, work is carried out to expand the range of compilers which will run Boost. Libraries included have to be maintained to remove bugs and also accomodate new compilers. There is always work in progress and it takes some time between approval of a new library and when it appears in a release.
Boost version 1.57.0 was released (3rd November 2014).
Release notes: www.boost.org
Boost version 1.56.0 was released (7th August 2014).
Release notes: www.boost.org
Boost version 1.55.0 was released (11th November 2013).
Release notes: www.boost.org
Boost version 1.54.0 was released (1st July 2013).
Release notes: www.boost.org
Boost version 1.53.0 was released (4th February 2013).
Release notes: www.boost.org
Boost version 1.52.0 was released (5th November 2012).
Special Note www.boost.org
Release notes: www.boost.org
Boost version 1.51.0 was released (20th August 2012).
Release notes: www.boost.org
Boost version 1.50.0 was released (28th June 2012).
Release notes: www.boost.org
Boost version 1.49.0 was released (24th February 2012).
Release notes: www.boost.org
Boost version 1.48.0 was released (15th November 2011).
Release notes: www.boost.org
Boost version 1.47.0 was released (11th July 2011).
Release notes: www.boost.org
Boost version 1.46.1 was released (12th March 2011).
Release notes: www.boost.org
Boost version 1.45.0 was released (19th November 2010).
Release notes: www.boost.org
Boost version 1.44.0 was released (13th August 2010).
Release notes: www.boost.org
Boost version 1.43.0 was released (6th May 2010).
Release notes: www.boost.org
Boost version 1.42.0 was released (2nd February 2010).
Release notes: www.boost.org
Boost version 1.41.0 was released (17th November 2009).
Boost libraries transform the Cee Plus Plus experience and are a major contributor to Late Cee Plus Plus's unique character.
It is interesting from the above list of releases that Boost has continued to develop over a long period. I think that the peer review process is an example of a working Community Of Trust of the sort which Jim Coplien wrote about on this wiki in 1996. -- John Fletcher
Libraries
There is a great wealth of cool libraries available here; Boost should always be double-checked before creating your own library. The libraries page boost.org lists the following categories. For more information, see boost.org .
String and text processing
Containers
Iterators
Algorithms
Function Objects and higher-order programming
Generic Programming
Template Metaprogramming
Preprocessor Metaprogramming
Concurrent Programming
Math and numerics
Correctness and testing
Data structures
Input/Output
Inter-language support
Memory
Parsing
Miscellaneous
Broken compiler workarounds
Library Pages on Wiki
Specific Boost libraries are described/discussed in the Wiki here:
Boost Mpl (MPL)
Boostu Blas (matrix template library)
Books on Boost
Books which discuss Boost libraries
Beyond The Cpp Standard Library ( Bjorn Karlsson )
Cpp Template Metaprogramming (book) discusses the Type Traits (Boost Type Traits), Template Metaprogramming (Boost Mpl) and Preprocessor Metaprogramming libraries.
The Cpp Cookbook gives examples of use of some of the libraries.
Boost Tools
There are series of tools which come with Boost to enable documentation and building of libraries and tests.
Needed Soon
See original on c2.com