Arabic Desert Sky provides helpful resources for learning both Modern Standard Arabic (MSA) and Egyptian dialect, including vocabulary lists and grammar lessons.
ArabiKey features a free Arabic keyboard which emulates the Windows Arabic keyboard. Its diacritization/tashkīl button will add the vowels to your text automatically. The site also provides lessons for Arabic-language learners.
Living Arabic has helpful resources for MSA and dialect learners alike with searchable dictionaries for Levantine, Egyptian, North African, Gulf, Iraqi, and Yemeni Arabic.
Online Diagnostic Assessment is an assessment tool developed by the Defense Language Institute Foreign Language Center (DLIFLC) to help foreign language learners evaluate and manage their learning.
Reverso allows users to search for relevant translations in context with real-life examples for millions of words and expressions, using natural language search engine applied on bilingual big data.
Alpheiois has created a chrome extension with tools to allow readers of Arabic online to click on words for definitions, translations, etymological analysis, and more.