There are quite a lot of spoken but unwritten languages. According to Ethnologue, 696 languages are known to lack scripts, and about 2,839 languages have no existing data.
The most common unwritten language is the sign language. Corinthian German also does not have an official written language.
Steps are being taken to write an official dictionary for all these languages.
Of all the languages out there that are spoken and not written, sign language is certainly the most common and most well known. Sign language uses signs of the hand to communicate. There is no written communication when it comes to sign language. Blissymbolics is another language that is only spoken and not written. One thing that is for certain is that these spoken only languages are very rare and linguists are constantly trying to learn more and more about these types of languages.
The development of these types of languages have been very popular over the past 50 years or so which has made the task of noting these languages a very hard thing to do. The one thing though is that these languages have been surviving and that is because of the people who opt to use the language and go out of their way to be able to preserve them.