I am of the personal belief that we humans have an ingrained need to worship. Something. Anything. It seems to me that there is an innate desire to seek out something greater and more powerful than ourselves, and turn to it as a source of inspiration and solace - or justification for our atrocities.
Religion fills that need. In an increasingly secular society, that need doesn't go away. Instead, people who turn their backs on religion, seem to fill that need with something else, and turn *it* into their religion. Human intellect, science, money, philosophical concepts, material goods, current trends, etc. - all these things have been used to fill that need.
So it was with interest that I found this speech from Michael Crichton on Environmentalism as Religion, written in 2003. It's a very interesting read.