There are many different brands of ouzo. In Greece by far the most popular and undisputed market leader is “Plomari” , with the sub-name of “Isidoros Arvanitis” to distinguish it from copy cats in the same region like Varvagiannis. Plomari – Isidoros Arvanitis (their official website is here – worth getting over the initial Flash hurdles for some good content) was started by the family that had made the famous (due to being in every Duty Free!) Ouzo 12. Unfortunately Ouzo12 was sold off to a multinational with many other drinks in their portfolio so it has fallen behind in most respects.
Ouzo is a traditional Greek drink so it is produced in small quantities all over the country.