There are probably tens of meta tags, eash SE has its own rules about meta tags, most of those are ignored...
Here is an example of some of the other meta tags that arent well know

<meta name="document-type" content="Public">
<meta name="document-rating" content="General">
<meta name="DC.LANGUAGE" content="English">
<meta name="doc-publisher" content="company name">
<meta name="Publisher" content="company name">
<meta name="topic" content="Internet Services,Web Hosting">
<meta name="document-classification" content="Business and Economy">
<meta name="classification" content="Business">
<meta name="content" content="Internet Services">
<meta name="DC.CREATOR" content="company name">
<meta name="DC.PUBLISHER" content="company name">
<meta name="DC.CONTRIBUTORS" content="company name">
<meta name="DC.Coverage" content="global">
<meta name="contactOrganization" content="company name">
<meta http-equiv="organization" content="company name">