Listservs are a low-cost way to get the word out about a new resource. To make the most out of notifying listservs of a new open resource, the author or publisher should already be relatively active on it. It might be frowned upon to simply advertise a new resource, rather than actually interacting with community. Authors are best positioned to reach out to listservs popular in their field, while librarians can notify OER and open access focused listservs. For librarians, OER publishers, and authors involved in open education, there are several OER specific listservs.
There may also be local OER listservs. For example, the Consortium of Academic and Research Libraries in Illinois maintains an OER Mailing list.