The message of Islam, as revealed by God to the Prophet Mohammed 1400 years ago, taught Muslims to love one another, respect the other Prophets, and pray five times a day to the one God, Allah. The crescent is often seen with a star or some other territorial identification
There are about 72 sects in Islam. The major ones being Sunnis and Shias. These are further subdivided, into many more sects. The holy book of the Muslims is the Quran (Koran) which is the same for ALL Muslims irrespective of their sects. This is a comprehensive link on the Quran http://www.winislam.com
Another common belief by ALL Muslims is the belief in 124,000 Prophets, all sent by God (Allah) to guide humanity. The first prophet being Adam, some others being Noah, Solomon, Lot, David, Jacob, Joseph, Abraham, Issac, Ishmael (Esmail ) Moses, Jesus, and lastly Mohamed.
There are several other common beliefs, like belief in the Hereafter, Day of Judgment, Angels etc. Therefore there is another site which discusses these in detail. especially the main differences between Sunnis and Shias. Also this site has articles in various languages. http://www.al-islam.org
There are also several lectures in English which can be downloaded or heard on line.