Get yer ApacheMods Here
Some very interesting and dynamic mods for apache listed at webthing.com.
mod_accessibility is particularly interesting.
It can be used with any Apache 2.0 server, and works as an output filter, transforming documents as they leave the server. This means it can be used with any content-generation software (such as CGI, PHP, mod_xml, or as a proxy server with mod_proxy) without any need for special configuration. It will of course also work with other output filters, such as an XSLT, character encoding, or encryption (SSL) modules.