Arabic has extremely many words, very few loan words and a grammar that was fixed before the invention of paper around 800 CE. Dozens of languages are influenced a lot by Arabic, not only Persian and Turkish, but also Swahili, Somali, Spanish, Urdu, Kurdish... Arabic used to be the lingua franca in the Middle East and the Islamic World at least from the tenth to the sixteenth centuries. Written Arabic is basically everywhere the same in the Arab World, but the dialects vary enormously: There is the Western group, Egyptian and the Eastern group, to say it shortly. There are some resources I remember and they will be linked here by and by.

Dict's:

Lessons

50 Languages has 100 chapters with ca. 20 sentences each. Combine any two languages. Plus Audios and extras.

Easy Arabic in the Egyptian, Tunesian and Palestinian dialects, with integrated Arabic (+ transcription) and English subtitles.

ArabicPod101.com with more than 1000 videos including readings, listening practise, grammar, words etc.

Learn with Safaa. 160+ vids on different topics

Videos, Films & More

Huge TED Talk collection in Arabic, some with subs

al-Jazeera Arabic, with link to live broadcast

Qutuuf al-adab min kalaam al-'arab, classic half-hour radio show

al-Idhaa'a l-Misriya, 5000+ vids, old radio shows

Kalimateen wa-bas, classic Egyptian radio show by Fuad al-Muhandis

al-kitaab al-masmuu', audio books

Arabic Collections Online (ACO) is a publicly available digital library of public domain Arabic language content.

Arabic for Nerds "A home for anyone addicted to Arabic."

بَرْغوث: أصغر أبطال الكرتون في التاريخ