There are too many unknown religions to really know how many there are. There are unknown peoples around the world and there are probably hundreds of religions nobody knows about. There are a few main religions that account for the majority of the world. Here's a quick list:
Christianity, Buddhism, Confucianism, Hinduism, Islam, Jainism, Judaism, Shinto, Sikhism, Taoism, even Voodoo. There are also many sub religions in each of these as well.
More religions include Neopagan faiths, Satanism, Scientology, Gypsies, Caodaism, and a host of others.
For more information on each other of these religions and more check out this site:
http://www.religioustolerance.org/
