NCSA Software Development maintains the CGI specification. You'll find the specification at the World Wide Web Consortium's CGI pages.
For CGI programming in C, a helpful library called cgic can be found here.
Site: Matt's Script Archive, Inc.
Find the justifiably famous Matt's Script Archive here. Look here first for tested, practical scripts in Perl and C for many common business uses.
Site: WWW Protocol Library for Perl
This is the University of California's public offering. Based on Perl version 5.003, this library contains many useful routines. ...