w3server is yet another HTTP server. It uses multi-threading and is very small. It does not support full HTTP 1.0, but it may be useful for other projects which just need a minimal HTTP server or for educational purposes. It was tested on an older Solaris system and on a current GNU/Linux system (Gentoo using Linux 2.6.15 and gcc 3.3.6).
GNU libmicrohttpd is a small C library for embedding HTTP server functionality into other applications. It is reentrant, fast, supports HTTP 1.1, and permits listening on multiple ports. The API is simple and still powerful enough to allow programmers to use the entire HTTP feature set. SSL/TLS support is available as an option.
The Darwin Calendar Server is a standards-compliant server that allows multiple users to collaboratively share calendaring information. It provides a shared location on the network to store schedules, and allows users to send each other and manage invitations. In order to provide interoperability with multiple calendaring clients, the server implements the CalDAV protocol, which is an extension of WebDAV, which is in turn an extension of HTTP.