mod_athena is an Apache-based application load balancer for large systems. It allows the HTTP server to act as a load balancer either internally to Apache's own mod_proxy (for reverse proxying), or externally to machines querying it. Arbitrary statistics are sent to the engine via a simple GET plus query-string interface, from which it will then make decisions based on chosen algorithms.
The mod_cidr_lookup is an Apache module for version 2.2 and 2.0. The mod_cidr_lookup detects client type by looking up the client's source IP address in CIDR blocks. This module sets the environment variable X_CLIENT_TYPE and the HTTP request header X-Client-Type, so it can be used in both Apache (httpd.conf) and Web applications.
mod_myvhost is an Apache module for dynamically configured name-based mass virtual hosting with PHP. Virtual host configurations and PHP settings are stored in a MySQL database. There is no need to have every vhost in apache's configuration file, or to restart apache after a configuration change. It is able to change PHP settings dynamically for any vhost. By default, it sets open_basedir as the vhost's rootdir, but you can change almost any parameter that exists in php.ini. For example, you can turn on safe_mode or register_globals for a particular vhost.