Online Dictionaries

http://en.mo3jam.com

User-generated Arabic dictionary, covering a wide range of Arabic dialects (Arabic only)

http://www.lisaanmasry.com/intro_en/index.html

English-Egyptian Arabic, including sections on grammar and pronunciation

http://www.livingarabic.com

English-Arabic dictionary, covering Egyptian, Levantine and Classical Arabic. Searchable by Arabic root and word, as well as English