Islam-Index
Introduction to Hadith--The Traditions of the Prophet Muhammad: Describes the criteria and processes through which the early Muslim community evaluated the reliability of these sayings.
Intro to the Shari'ah: Describes the sources and legal strategies through which the Islamic law was formed.
Stunningly Brief Introduction to Sufism: A brief and dirty overview of a 1200 year old phenomenon that has developed in differently in different Islamic contexts.