Web tool retrieves hosting software information from any domain name. No longer maintained, but possibly of historical interest. Free trial version, manual, mailing lists, news.
Plexus is a public domain http server written in perl.
Also a comprehensive survey of webserver software usage. Basic explanation of theory and implementation. Free binaries, a powerful API, Tcl built-in, strong DB access tools. The world's most scalable high performance web server software, providing solutions for content providers, ISP hosting, intranets and secure e-commerce with comprehensive support. For Unix and NT servers.