A complete framework
to create and run Web applications
Eliom

Write client/server Web applications in very few lines of OCaml code!
Js_of_ocaml

An OCaml to Javascript compiler.
Lwt

A cooperative threading library for OCaml.
Ocsigenserver

A full-featured and extensible Web server.
OClosure

An OCaml binding of the Google Closure widget library.
Macaque

A language for type-safe database queries.
Most projects can be used independently.
For more information, and learn how to write a sample application, have a look at the tutorial.
Also refer to the documentation of each project to learn more about it.