fhttpd is an FTP/HTTP server with modules support. Modules run as separate "looping" processes locally or remotely, and can be configured to run under separate userids. Locally running modules can be configured to use fd passing of client's connection to avoid overhead in sending the response. ~username URL to directory remapping is supported in HTTP, and can be configured to access files, run scripts and modules under mapped user's userid.
Sambuca is a Java HTTP server framework that allows developers to embed an HTTP server directly in their applications with custom HTTP request handlers, so that their application can directly process incoming HTTP requests and easily send back HTTP formatted responses to the requesting client. Applications can host standalone HTTP services such as Web Services without having to deploy and integrate with a full application server such as Tomcat, JBoss, or WebLogic.
HN URL Rewrite can emulate page request URL rewriting and redirection. It can parse and change the output of the current page script to rewrite the URLs of links or images in the page with absolute URLs, relative URIs, and URLs that contain the scheme and host (http://www.somehost.com).
mod_auth_cache transparently caches an authentication originally done by a different module. The aim of this module is to speed up complex authentication mechanisms, to reduce database traffic if authenticating thru a backend database, and to implement some sort of authentication reliability if the database server fails. As the caching is completely transparent (done by the webserver), you don't have to change or implement new functions in your existing applications. The module only caches a users authentication and not a users access permissions, which can still be controlled by a different module.