Islami City
Islami city.com: Educational Addendum Understanding
This site provides you with the nature of Islamic law and all of the major aspects of it. Excellent reference for basic Islamic terms.
Internet History Sourcebooks Project
Fordham University: Medieval Sourcebook: Battle of the Yarmuk
This site from Fordham University provides an early writing describing the battle of Yarmuk, at which the Muslims defeated the Byzantine Emperor Heraclius and his army.
Other
The Muslim Students Association: Oneness of God
This page is about the fundamental Islamic belief that there is only one God. Provides examples from the Quran on other descriptive names that refer to God.