Mod_auth_kerb is an Apache module designed to provide Kerberos user authentication to the Apache web server. Using the Basic Auth mechanism, it retrieves a username/password pair from the browser and checks them against a Kerberos server as set up by your particular organization. It also supports mutual ticket authentication, although most browsers do not support that natively.
mod_proxy_add_forward.c is an Apache module that adds a 'X-Forwarded-For' header to outgoing proxy requests like Squid does. You can then get the client IP back on the proxied host by setting r- >connection->remote_ip from this header. It's very useful for the common lightweight frontend/heavy backend mod_perl setup.
Naridesh is a Web server written in Perl. It supports directory browsing, username/password security, file download, and plugins. It has some limited support to turn off file downloading, and directory browsing. Naridesh can also send the "index.html" file or equivalent if it is found in the directory, and also supports files that are symlinks to URLs.
JWAA is a software framework for building dynamic Web applications as networks of first-class Java objects. XML is used for representing information normally coded as HTML. The XML files are automatically reloaded when they change. It has a "persistent forms" feature in which form data automatically persists in the database such that fields behave like pieces of paper that automatically preserve what's written on them. This default behavior is easily overridden. Invalid links are reported at XML load time via the browser, and are also recorded in log files.