Dr. Clue's CGI reference including C++ code  
   Information covering how CGI works and the different methods of interaction. Includes a free C++ class that compiles on both Unix and Windows , along with several pieces of code that exploit it. The base classes themselves are generally useful too.
   http://www.drclue.net/F1.cgi/HTML/CGI/CGI.html

VBMcgi  
   A free multiplatform library in C++ that isolates the work of webmaster and webdesign. That is, The webmaster can use C++ and VBMCgi, and join a team with a "standard" webdesigner.
   http://www.vbmcgi.org/

HotScripts.com: C and C++  
   Directory of books, tips, tutorials about C++ CGI programming. Site has a large collection of scripts.
   http://www.hotscripts.com/C_and_C++/

JWCGI  
   A C++ library for creating CGI applications. (Linux/Windows compatible) [Open source]
   http://www.johnwiggins.net/johnwiggins/code/jwcgi/

The open core (oc) web class library  
   Written in C++, the oc library has been continually enhanced since 1996. It performs all communication with the httpd server and browser, can handle file uploads and has an abstraction layer for all database servers. [Open source]
   http://www.w3sys.com/pages.meta/code.html

C++ CGI Parser Library  
   For accessing HTTP form data, path info, and cookie data from CGI applications. In addition to normal GET and POST data, the component supports file uploads (multipart/form-data), and simple xml content types (text/xml) - allowing easy use with xml based
   http://www.rudeserver.com/cgiparser/