Hi, Wordsmith. I am a Muslim. Islam does not have a specific ceremony or rite of passage that takes one from childhood to adulthood. The age of puberty (which varies from person to person), however, is considered the age at which one becomes accountable to God for religious duties such as praying the five daily prayers on time and fasting the month of Ramadan. It is also the age at which one becomes accountable for any sins committed. According to Muslim teachings, parents divide their treatment of children into three stages:
Birth to age 7: focus on play and the fun of childhood while still laying the foundations for later stages of education
Age 7-14: focus on teaching correct behavior, gradually preparing children for the responsibilities of life - it is during this period that most children begin praying, fasting, etc.
Age 14-21: treating our children like friends, advising them when needed, etc.
After the last stage, we are advised to leave them on their own. This does not mean abandonning them, living separately, or failing to advise them, but having respect for their decisions in life and letting them mature into adults.
Circumcision is required of Muslim boys/men but often takes place shortly after birth. Some cultures make this into a ceremony, but the party itself is not based in Islam. There is no party/ceremony needed or required.
When someone converts to Islam, he or she should pronounce the shahada (a testimony of faith). Again, some people make this into a formal ceremony, including witnesses, but this is not a requirement of Islam. Shahada can be a personal matter between the individual and God. After declaring the shahada, one does a full-body ablution called ghusl and begins life as a new Muslim. Ghusl is also required after menstruation and intimate relations.
The shahada is offered with every prayer, but most people born into Islam may say it again after reaching maturity and begin to practice faith out of personal conviction and belief rather than because of culture or family tradition.
Besides marriage, the one "ceremony" I can think of is called aqeeqah, which takes place after a baby is born. This involves giving meat to the poor in thanks to God for the birth of the newborn. Here is a little information on that:
http://www.islamonline.net/servlet/...h-Ask_Scholar/FatwaE/FatwaE&cid=1119503546908
There are also the rites of Hajj, which every Muslim should strive to fulfill once in a lifetime.
I also wanted to point out that Islam falls into the category of Abrahamic faith, along with Judaism and Christianity.