By the 18th century, different types of Te (hand) had developed in three Okinawan villages: Naha, Shuri, and Tomari. The styles were named Naha-te, Shuri-te and Tomari-te, respectively.

The successor styles to Shuri-te include Shotokan (Japanese Karate style since this is the style Gichin Funakoshi introduced to mailand Japan), ****ō-ryū, Shōrin-ryū, Shudokan, Shōrinji-ryū, and Motobu-ryū.

The successor styles to Tomari-te include Motobu-ryū, Matsubayashi-ryu and Shōrinji-ryū.

The successor styles to Naha-te include Gōjū-ryū, Uechi-ryū, Ryūei-ryū, and Tōon-ryū.

Notice that there are some overlaps in the styles as some masters trained in more than one style.

Edit: HA! It bleeped Shito-ryu. LOL How dumb can this get!!!!

Liondancer beat me to it.

Uechi Ryu, Goju Ryu, Shorin Ryu and Isshin-ryū are often called the core 4 Okinawan styles of karate. But what Liondancer posted is a more accurate answer as it gives more of the lineage.

Also note that of the styles, Uechi Ryu developed on a path that was more on it's own. In some ways this means that Uechi is closer to it's Chinese roots than the other styles. But that's a long discussion and not something that would fit in the limits of space here

There are no real "main styles" of Okinawan Karate..

Shurite/Tomarite = Shorin Ryu and its many branches.

Nahate = Goju Ryu, Uechi Ryu..

These are the most popular styles.

There are also styles like Motobu Udunti - Motobu Family Palace Hand

To'on Ryu - considered a Nahate style.

Kingai Ryu...

Shito Ryu

Chito Ryu