SO/IEC  JTC1/SC22/WG21 is the international standardization working group for the programming language C++.

The current C++ standard is ISO/IEC 14882:2017 (C++17). The standard, which describes the core language and the standard libraries, must be bought from ANSI, ISO, or the BSI. Here we present the available draft, and thus free, versions of the standard.

Available C++ Standard Drafts and Related Documents

The working draft standard for C++17 is N4659 (from isocpp.org) (local).

The closest available draft for C++14 would seem to be  N4140 (original from github.com).

For C++11, the WG21 site gives N3242 (original from WG21) as a draft C11 standard, dated 28 February 2011.

There are some drafts for C++98, the first ISO C++ standard, but they are not from the WG21 site.

From the BABAR there is The 1997 Public Review Document (local), also referenced as WG21/N1043 and dated December 1996. N1043 is available as a set of PDF files (local) from the same site.

C++98 [ISO/IEC 14882:1998(E)] - From www.kuzbass.ru (local) there a document called 'Final Draft', dated May 1998. A PDF version is available from plumber.gnu-darwin.org (local), dated September 1998. There is also a Proposed Defect Report on ISO/IEC1488:1998 (local) from WG21.

Useful Sites

The Wikipedia articles on C++11, C++14 and C++17 give overviews of the changes from previous versions.

There is an interview about C++17 with Bjarne Stroustrup at InfoQueue; and Egor Bredikhin's blog describes  C++17 features.

There is a C++14 overview in Dr. Dobb's Journal 16 September 2014.

There is a good language reference that covers C++11, C++14 and C++17 features at cppreference.com.

Bjarne Stroustrup C++ link on his home page is worth a visit. In particular, he has written a general C++ FAQ, and has given his thoughts about what C++17 should be in N4492. There also a good C++ FAQ at isocpp.org.

Frank B. Brokken's C++ Annotations is a general C++ tutorial. You might find The programmer's Guide to C++ of some use, although it it rather out of date (1997).