As the world moved into the 60s and 70s, two things started happening to Wicca. The first is that it began spreading beyond the borders of England. This is not to say that American Witches did not exist before the 70s, but the Wiccan movement did start in England and it wasn't until later that a Witchcraft boom started in America. The second thing that happened is that people started becoming Wiccan without joining covens. They became Solitaires or Solitary Practitioners; people who practiced alone.
The Solitary movement began out of necessity. People read the books of Murray, Gardner, and others such as Alexander and Crowley, and wanted to become Wiccan but were unable to find others around them who felt the same. Realizing that what mattered was their beliefs, these people adopted the Wiccan religion anyway, waiting until a coven became available to them.
After these people started practicing alone, people realized that one shouldn't feel obligated to practice in a coven. Some people preferred to practice alone, and began choosing to even when a coven was available to them. This is when the Solitary movement really started; when people began forming their own personal versions of Wiccan spirituality.
An explosion of knowledge occured after the beginning of the Solitary movement, and books about Solitary Wicca hit presses everywhere. Many authors such as Silver RavenWolf, Laurie Cabot, the Campienellis, and especially Scott Cunningham and his Wicca: A Guide for the Solitary Practioner, are considered teachers or mentors by people who have never even met them.
The Solitary movement changed the way that Wiccan was practiced. If you compare our generation of Witches to the generations of the past, you will find that Wiccans of thepresent, are far less likely to be involved with a coven, they focus less on the fertility aspect of the religion and more on ecology, and they are more theological and less ritual-oriented. It has become a more welcoming, intellectual, morality-based religion, and a less exclusive, physical religion. There are many different kinds of Wiccans as a result of these changes: there are still traditionalist Gardnerians and Alexandrians, Dianic Wiccans, Wiccans who heavily incorporate Native American beliefs into their spirituality, Celtic Wiccans, Eclectic Solitaries, and even Christian Witches--people who believe in Jesus Christ's divinity but who also revere nature and practice magic. We are very diverse, but we also enjoy a very warm fellowship.