After my post yesterday about a language learning blog, reader Mohammad Taha commented that the University of Maryland National Foreign Language Center has an online portal with language learning materials, including Arabic dialects. Though access is by subscription, you can browse the available courses.
While we're on the subject, it's worth noting for those who may not know that the old Foreign Service Institute (FSI) language courses are public domain and that they include books and, on some online sites, tapes for learning a wide variety of languages,including, for Arabic, Written Arabic, Levantine Arabic, and Saudi Arabic (Urban Hijazi Dialect). There are also courses in Spoken Persian, Turkish, and Hebrew, and some online sites include audio files of the tapes.
You can also find online courses from the Peace Corps and the Defense Language Institute online, offering an even broader range of dialect studies.
And speaking of FSI, let me plug two little FSI booklets from the 1970s by Margaret K. Omar (Margaret K. Nydell) that I personally found valuable back in the day.
From Eastern to Western Arabic, a 47-page guide for persons familiar with either Egyptian or Levantine Arabic and are tying to learn Moroccan, which at first seems impenetrable to those familiar with eastern dialects. As an introduction, it can be quite useful, and I used it before my first trip to Morocco.
Levantine and Egyptian Arabic: Comparative Study. Again it is only 50 pages but is intended for someone familiar with either Levantine or Egyptian and seeking to approach the other. Neither of these little books is a course or a descriptive grammar, but they are useful beginner's guides for those tying to navigate between dialects.