Madinah Arabic is most suitable for learners focused on classical Arabic. It has text-based lessons for beginners and quizzes for intermediate learners. Although the interface is not very modern, it gives a decent introduction to the Arabic script, in addition to basic sentence structures with native speaker pronunciation for every word.
After learning the basic script, there are over 100 step-by-step beginner lessons that start with practical sentence structures. Instead of learning basic phrases, such as how to order food at a restaurant, you will learn how to build your own sentences. There are a few fill-in-the-blank and multiple-choice questions in the lessons, plus about 90 beginner to advanced quizzes to test listening and reading comprehension. The site also offers Arabic tutors over Skype with a free trial lesson.