Hi all, im trying to make an up to date chart of meta tags, for all of us, with their purposes, their use and their good (or bad) effects on search engines/being found. Also any body knows new/promising meta tags? I will add yours into my list so this chart is a result of live discussion and up to date. Also, it would be creative to invent your own useful meta, because we are the ones making the web, or aren't we?

LEGEND
P PURPOSE? What does this meta tag do in 2011, if anything
N NECESSARY? Does every site really needs it or not?
G GOOD wether it will have a good effect for your site to be found
I INVENTED meta tag, who knows it will be accepted in a year!

META "METANAME" = PURPOSE?   -   NECESSARY?   -   GOOD EFFECT?

#### important
meta "title" = P consice summary + teaser - N very - G extremely
meta "description" = P description + teaser - N yes - G very
meta "robots" = P if needed, to skip default dmoz/yahoodir listing - N no - G?

#### new & promising! Thanks for input (John, )
meta "original-source" P url of whoever broke the news gets credits - N? - G?
meta "syndication-source"  P url for syndication of published news - N? - G?
meta "canonical" P? - N? - G?

#### seems obsolete
meta "keywords" = P some keywords - N+G not for google but yahoo likes them
meta "language" = P overrule guesswork by defining language - N no - G? 
meta "page-topic" = P topic/theme - N? - G?
meta "abstract" = P short summary - N? - G?
meta "copyright" = ?

#### invented by me
meta "audience" = P filteres audience: "+seniors, +parents, -children, -youth"
meta "mood" = P specifies textual style: "discussion, informative, commercial,
              sexual, fictional, scientific, romantic, therapeutic, technical"