Regular quizzes about the Arabic language: about vocabulary, grammar, إِعراب, history, and proverbs - on Arabic for Nerds. For free.
Many websites offer free Arabic lessons. Two of the best are Playaling and material of the Defense Language Institute.
In Arabic, there is a special type of masdar which focuses on the number of times. It is called ism al-Marra (اسم المرة).