The official OCaml mailing list: caml-list AT inria.fr
The OCaml mailing list is intended for all users of the OCaml implementations developed at Inria. The purpose of this list is to share experience, exchange ideas and code, and report on applications of the OCaml language. This list is not moderated, but posting is restricted to the subscribers of the list. Messages are generally in English but sometimes also in French. In 2010, the list has about 1500 subscribers, who exchange about 300 messages per month.
OCaml Beginners mailing list: ocaml_beginners AT yahoogroups.com
This list is a place for the mutual aid of those who recognize that they're not OCaml gurus yet... everything you wanted to ask about OCaml, but were afraid to submit in the more official caml-list AT inria.fr, can be asked, answered and discussed here. In early 2004, the list has about 300 subscribers, who exchange about 100 messages per month.
OCaml jobs and internships mailing list: ocaml-jobs AT inria.fr
This list is for exchanges between people looking for a job or an internship requiring skills in OCaml and people, corporations, universities, ..., offering such jobs or internships.
Annoucements about OCaml: caml-announce AT inria.fr
This is a low-traffic, moderated list for announcements of OCaml releases and new OCaml-related software, libraries, documents, etc.
OCaml IRC Channel: irc.freenode.net \#ocaml
This is real-time communication channel, where you can ask for help. There are about a hundred users hanging around; don't ask if you can ask, just ask, and be patient: not everyone is in the same timezone. The IRC Channel can be accessed through a web interface or any regular IRC client.
Discussion group about ML: comp.lang.ml
This is a moderated Usenet newsgroup about all variants of ML. Discussions generally concerns Standard ML implementations (such as SML-NJ), but some threads concerns the OCaml branch.
Discussion group about functional languages: comp.lang.functional
This is an unmoderated usenet newsgroup for the discussion of all aspects of functional programming languages, including their design, application, theoretical foundation, and implementation. Discussions concern all families of functional programming languages including non-strict ones (e.g. Haskell) and strict ones (e.g. Scheme, SML or OCaml).