Ocsigen is an extensible Web server. This means that you can plug modules into the server, to serve several kinds of pages. A few extensions are provided with the official Ocsigen distribution:

Staticmod
is an extension to serve static files.
Eliom
is an extension to create dynamic Web site in OCaml using high level concepts.
Extendconfiguration
allows for more options in the configuration file.
Accesscontrol
allows to restrict the access to the sites from the config file (to request coming from a subnet, containing some headers, etc.).
Authbasic
allows to restrict the access to the sites from the config file using Basic HTTP Authentication.
CGImod
is an extension to serve CGI scripts. It may also be used to serve PHP through CGI.
Deflatemod
is an extension used to compress data before sending to the client.
Redirectmod
is an extension to set redirections towards other Web sites from the configuration file.
Revproxy
is a reverse proxy for Ocsigen. It allows to ask another server to handle the request.
Rewritemod
is a module to rewrite requests.
Outputfilter
allows to rewrite some parts of the output before sending it to the client.
Userconf
allows users to have their own configuration files.
Comet
makes server to client communications possible.