The following summary of safe and unsafe solar viewing techniques comes from
NASA's eclipse guru Fred Espenak:

(http://sunearth.gsfc.nasa.gov/eclipse/SEhelp/safety.html):

Generally, the same equipment, techniques and precautions used to observe
the Sun outside of eclipse are required for annular eclipses and the partial
phases of total eclipses. The safest and most inexpensive of these methods
is by projection, in which a pinhole or small opening is used to cast the
image of the Sun on a screen placed a half-meter or more beyond the opening.
Projected images of the Sun may even be seen on the ground in the small
openings created by interlacing fingers, or in the dappled sunlight beneath
a leafy tree. Binoculars can also be used to project a magnified image of
the Sun on a white card, but you must avoid the temptation of using these
instruments for direct viewing.

The Sun can be viewed directly only when using filters specifically designed
for this purpose. Such filters usually have a thin layer of aluminum,
chromium or silver deposited on their surfaces that attenuates ultraviolet,
visible, and infrared energy. One of the most widely available filters for
safe solar viewing is a number 14 welder's glass, available through welding
supply outlets. More recently, aluminized mylar has become a popular,
inexpensive alternative. Mylar can easily be cut with scissors and adapted
to any kind of box or viewing device. A number of sources for solar filters
are listed below. No filter is safe to use with any optical device (i.e. -
telescope, binoculars, etc.) unless it has been specifically designed for
that purpose. Experienced amateur and professional astronomers may also use
one or two layers of completely exposed and fully developed black-and-white
film, provided the film contains a silver emulsion. Since all developed
color films lack silver, they are always unsafe for use in solar viewing.

Unsafe filters include color film, some non-silver black and white film,
medical x-ray films with images on them, smoked glass, photographic neutral
density filters and polarizing filters. Solar filters designed to thread
into eyepieces which are often sold with inexpensive telescopes are also
dangerous. They should not be used for viewing the Sun at any time since
they often crack from overheating. Do not experiment with other filters
unless you are certain that they are safe. Damage to the eyes comes
predominantly from invisible infrared wavelengths. The fact that the Sun
appears dark in a filter or that you feel no discomfort does not guarantee
that your eyes are safe. Avoid all unnecessary risks. Your local planetarium
or amateur astronomy club is a good source for additional information.

In spite of these precautions, the total phase of an eclipse can and should
be viewed without any filters whatsoever. The naked eye view of totality is
completely safe and is overwhelmingly awe-inspiring!