If you administer a nonprofit or community organization or a government agency, you can post every type of listing: jobs, internships, volunteer opportunities, and events. Businesses can post every listing type except volunteer opportunities. Recruitment firms are not eligible to post events.
If you administer more than one organization, make sure to select appropriately from the list on the posting page. If you want to post on behalf of an organization that's not listed on Idealist yet, just register it! Be sure to search for it first though—a lot of organizations are already listed in our database.