In the United States, Arabic speaking communities are considered extremly important in ethnic TV both on line and in cable, as they are usually holding the lion share of subscribers base in those mediums.
Eyoon is a web directory for Arabic websites. Started in 1995. Mainly focusing on Arabic speaking countries
Araby is a new search engine that index arabic websites. Moreover, they index images, and blogs
4arab.net is another search engine. The indexed sites are still limited
Nesnas, which means "Monkey" is a large portal and search engine fo Arabic websites.
Arabiks is a small index, but it provides a CPC advertizing option
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Ayna seems to a winner, in terms of indexing as well as provided portals services.