Erlangopenid is a project mainly written in Erlang, it's free.
An Erlang OpenID module
An Erlang OpenID module.
Currently implements OpenID 1.1
To use, you call start_authentication with the claimed identifier and a URL to return to, then redirect to the returned URL.
Upon return, pass a proplist of your GET parameters to finish_authentication, and you will get back {ok, Identifier} or {error, Error}.