Something like 100 languages have written form to go with them. The other 6800 that remain on Earth are spoken-only.
This visual represenation of the biggest number of language speakers includes some explanation and discussion.
Seeing the reverse - least number of speakers - in visual form wold be good, too!
One of the easily overlooked features of the (English language) Wikipedia is the sidebar at lower left in which a given topic is shown with hotlinks to all the other language-versions of Wikipedia, when that topic is also available there. Some subjects have lots of corresponding articles; others have few. In some cases the biggest number of Wikipedia articles (found in English, Dutch, German) provide outline and some content for the other languages. But in other cases the article is composed from scratch, using supporting documents of that other language, with little or no reference to the English or another source article.