Local vs Foreign Sites
The most frequent sites in Saudi Arabia are generally local sites. This is partly due to their culture in the country, one of the deciding factors is due to the language. As most Saudi Arabian converse in Arabic, their sites surfing are also influenced by this factor. And hence, only these local sites are able to provide them with the luxury of surfing in Arabic.

Popular Foreign Sites
After some research, we discovered that there are also some popular foreign sites in Saudi Arabia;

Google.com
Yahoo.com
Hotmail.com

For the whole list of the most popular sites in Saudi Arabia, please proceed to the below link;
http://www.internet.gov.sa/resources/statistics/most-visited-sites-in-saudi-arabia