Modern skepticism is an approach to life that demands evidence and reason for beliefs and practices. Skeptics may be best known for debunking stories of the paranormal — like ghosts, psychics, UFOs, Bigfoot, and the Bermuda Triangle — and of pseudosciences, such as alternative medicine and creationism. But skepticism can be beneficially applied to all human experience from the mundane to the profound.
An illustrated introduction to skepticism:
III.
What to answer when they say... 
The first response to an unsubstantiated claim from a believer,
of course, is "What's your evidence?" Beyond that though, there
are certain dubious arguments that come up time and again from honest
believers and charlatans alike. Here's what skeptics can say to dispense
with these bogus points.
Skeptical Quotations
Famous and not-so-famous words about belief and skepticism from
skeptical and not-so-skeptical thinkers and writers.
Skeptical links
Sites to find out more about the movement for critical inquiry.