Note: The list of contributors is getting long for the "editing reason" line, so I'm putting the name of the contributors here: Thanks, Taalib, Josh, Haroon, pcopti, kopo, Wadi Hanifa, Long_Tall_Texan, Abu Talha, tr463, نهشل بن شداد , Barkoosh and Paxos 
Dictionaries and Glossaries
2a.1 Mawrid Reader (a single search, by root letters for example "k t b", for the contents of 27 printed dictionaries, including Hans Wehr, Lane's Lexicon, Hava, Al-Munjid, and Badawi/Hinds)
2a.2 Almaany.com (Arabic-English, English-Arabic, including new words not found in traditional dictionaries)
2a.3 Glosbe (multilingual dictionaries based on bilingual corpora)
2a.4 Reverso Context (multilingual dictionaries based on bilingual corpora)
2a.5 The Quranic Arabic Corpus (for the meaning, morphology and frequency of use of each word in the Qur'an)
2b. Babylon English-Arabic Dictionary - Babylon
(English-Arabic)
2c. Arab2English Dictionary - Babylon
(Arabic-English)
2d. Dictionary - Babylon
(German-Arabic)
2e. قاموس معاجم اللغة: معجم عربي عربي Arabic monolingual dictionaries لسان العرب، مختار الصحاح، المعجم الوسيط، تاج العروس، الصحاح في اللغة
2f. http://www.alburaq.net/dictionary1/transform.cfm
(Arabic-English)
2g. ECTACO - Electronic Dictionary, Handheld Electronic Dictionaries, Electronic Translator, Translation Software, Ebook Reader. - ECTACO
(Arabic-English, English-Arabic)
2h. Arabic-English Lexicon by Edward William Lane
2h1.free Lane Arabic English Lexicon / Dictionary
2i. Trade Forex | CFDs Trading | Options | Easy Forex | easyMarkets
(English-Arabic dictionary for commerce & stock market terminology)
2j. http://www.lessan.org/web/all.jsp
(Arabic<>German, Arabic<>English, Arabic<>Spanish)
2k. http://www.mpm.gov.ma/documentation/terminologie_maritime.htm
(French-Arabic glossary of maritime terminology)
2l. English - Arabic Glossary: Finance
(English-Arabic finance glossary)
2m. http://www.saccourt.com/geninfo/legal_glossaries/glossaries/Arabic_English_Legal_Glossary.pdf
(English-Arabic legal glossary)
2n. arabsun.de
(Arabic-English-German, all directions; German interface)
2o. English-Arabic Dictionary - Index
(English-Arabic)
2p.
WHO EMRO | WHO EMRO | Unified Medical Dictionary
(The unified medical dictionary of the WHO glossary, Arabic-English-French-German)
2q.
العيادة الشاملة :: Click4clinic.com ::
(medical glossary, both directions)
2r.
Medicine English-Arabic Dictionary - Babylon
(medical glossary, English-Arabic)
2s.
Unified Dentistry Dictionary Dictionary - Babylon
(dentristry glossary, English-Arabic)
2t.
Dictionary - Babylon
(economic glossary, English-Arabic)
2u.
English 2 Arabic Glossary Dictionary - Babylon
(glossary of phrases and rare words, English-Arabic)
2v.
Wadan English-Arabic Auditing Terms Dictionary - Babylon
(glossary of auditing terms, English-Arabic)
2w.
الباحث العربي: قاموس عربي عربي (Arabic-Arabic dictionaries)
2x.
www.investing-glossary.com
(financial and investing glossary: English-French-Arabic or French-English-Arabic, with explanations in Arabic of the Arabic translations)
2y.
http://web.ifac.org/download/translation_db_file_01.pdf
(glossary of auditing terms, English-Arabic)
2z.
http://www.arabization.org.ma/Dictionnaire.asp
(Arabic-French-English, glossary of field-specific terms, searchable, Arabic interface)
2aa.
http://unterm.un.org/dgaacs/arabterm.nsf
(UN terminology; English-Arabic-French-Spanish)
2bb.
http://www.arabdictionary.huji.ac.il/
(Arabic-Hebrew, both directions)
2cc.
http://www.dictionarybay.com/en_ar.aspx (Arabic-English, both directions, with specialized dictionaries).
2dd.
Mo3jam: Dictionary of colloquial Arabic / Arabic Slang (user-generated dictionary of colloquial Arabic; interface in English and Arabic).
2ee. xxxx Dead link removed.
2ff.
باسم - بحث عن مصطلح technical terminology in different fields. In Arabic, English, French and German.
2gg.
Arabic-English dictionary for the use of students : Hava, J.G : Free Download & Streaming : Internet Archive
(Hava's Arabic-English dictionary. Very helpful for classical Arabic, but not much good for MSA.)
2hh.
Aratools Arabic-English Dictionary
(Arabic-English dictionary, gives prefix and suffix morphology and shows POS information).
2ii.
Search and Download International Terminology - Microsoft | Language Portal (IT and computer-related terminology from Microsoft.)
2jj.
Dictionnaire Français-Arabe en ligne - Larousse (French-Arabic dictionary).
2kk.
http://www.acmls.org/Dictionary/Abb_search.asp (Medical accronyms. English-Arabic)
2ll.
2014. The Arabic Dialect of Benghazi (Libya): Historical and Comparative Notes E-Book about the dialects of Benghazi (Eastern Libya).
2mm.
http://scans.library.utoronto.ca/pdf/5/32/dictionnairefran00abaluoft/dictionnairefran00abaluoft.pdf French-Arabic dictionary (Alegrian Arabic)