Libwww - the W3C Protocol Library
Libwww is a highly modular, general-purpose client side Web API written in C for Unix and Windows (Win32). It's well suited for both small and large applications, like browser/editors, robots, batch tools, etc. Pluggable modules provided with libwww include complete HTTP/1.1 (with caching, pipelining, PUT, POST, Digest Authentication, deflate, etc), MySQL logging, FTP, HTML/4, XML (expat), RDF (SiRPAC), WebDAV, and much more. The purpose of libwww is to serve as a testbed for protocol experiments.
This is a complete mirror of the W3C libwww repository.
For more info, see http://www.w3.org/Library/