Islamic sects are not simply "denominations," if that word is understood to mean various valid approaches to the same religion. Members of one Islamic group do not usually recognize members of other groups as fellow Muslims, and open conflict between sects is not uncommon.
Yet, as a whole, Islam is less divided than Christianity and Judaism - the vast majority of the world's Muslims are Sunnis. And Sufism is a mystical approach to Islam that is approved as orthodox by nearly all Muslims. Follow a link below to learn about some of the largest Muslim sects and groups.