http://ocsigen.org/lwt/manual/ http://projects.camlcity.org/projects/dl/ocamlnet-3.7.4/doc/... https://blogs.janestreet.com/announcing-async/
For example you can use them to write HTTP services/clients that scale to lots of concurrent connections without blocking, and the code you write is not that much different from the one you'd write in direct-style.
