Sociologists say about 20 new religions pop up each year in the United States. Some survive; some live only for a season. Worldwide new religions make up less than 2% of the population.

Sociologists have claimed that such movements satisfy the psychological and social needs of young people seeking a meaning for life which they cannot find in the mainstream religious traditions. Some are referred to as cults. Some examples are:

• Unification Church ('Moonies') - Founded by Korean religious leader Sun Myung Moon in 1954. It includes belief in a universal God; in striving toward the creation of a literal Kingdom of Heaven on earth; in the universal salvation of all people Church membership is estimated to be several hundred thousand to a few million.
• Scientology - Started in New Jersey in 1942 by L. Ron Hubbard as a successor to his earlier self-help system, Dianetics. Scientology teaches that people are immortal spiritual beings who have forgotten their true nature. Thru their practices a Scientologist may progress toward the Clear state, winning gradual freedom from the reactive mind's engrams, and acquiring certainty of his or her reality.
  Scientology and wikipedia have been having a battle over what wikipedia says is "pushing its own agenda on the site", so they have been banned. See SciTechBlog and wikipedia
  (25,000 U.S.) See How many Scientologists are there?
• Divine Light Mission (DLM) - Founded in 1960 by guru Shri Hans Ji Maharaj for his following in northern India.
• The Black Muslim Movement or Nation of Islam was founded in 1930 in Detroit by Wallace D. Fard and led by Elijah Muhammad. The Movement expanded greatly in the 1950s when Malcolm X became one of its spokesmen. Mainstream Muslims consider the group an independent religion that has adopted Islamic terminology rather than an Islamic sect due to differing beliefs about God, race, and prophecy among others. in 1976 it split into the American Muslim Mission and the radical Nation of Islam, led by Louis Farrakhan. A 2003 article at BelieversWeb.org says: "The hard core of the Muslims in the United States is probably around 35,000. But they have more than 84 temples, and a membership goal of 20,000,000 in the United States."
  (150,000-250,000)
• The Hare Krishna movement based on the Vaishnavite philosophy was established in America in 1965, with the official name International Society for Krishna Conciousness (ISKCON). It has only about 250,000 adherents, which were visible in airports and large cities in the 70's-90' chanting with their saffron robes and shaved heads.
• The Jesus Movement - A Christian movement beginning on the on the West Coast of the United States in the late 1960s and early 1970s and spreading primarily through North America and Europe, before dying out by the early 1980s.
• Children of God - Started in 1968 in Huntington Beach, California, United States. It was an offshoot of the Jesus movement of the late 1960s, with many of its early converts drawn from the hippie movement.
• The Toronto Blessing - Started in 1994, it has become known for ecstatic worship, including what is known as falling or resting in the Spirit, laughter, shaking, and crying. It has since faded from public view.
• Soka Gakkai - A modern version of Buddhism. Brought to the United States by Japanese war brides, and in the 1960s, it caught on with hippies. Now it has more than 300,000 adherents in the United States, most of them middle class, from all ethnic groups.
• Religions based on revitalised Shintoism in Japan
• Wiccan/Pagan/Druid, or witchcraft, among young people. Teens seem to be drawn to Wicca.
• Rastafari movement - Started in Jamaica, its adherents, who worship Haile Selassie I of Ethiopia, former Emperor of Ethiopia. (600,000)

New Age Religion is not really new and usually not included in New Religions. It is not a religion at all, but a vast syncretism (or mixing) of numerous religious and philosophical ideas. It has some similarities to ancient Gnosticism.

Links:
New Religions and Academic studies of new religions at ReligiousTolerance.org
New Religion in America : NPR
New religious movement - Wikipedia, the free encyclopedia