When Venus comes directly between the Earth and the Sun, it is called a transit. During the transit, the planet Venus blocks out a portion of the Sun's image, appearing as a black dot on the face of the Sun. Over time, the black dot moves into the Sun's disk, travels across the face of the Sun (transits), and exits out another edge. Here is a map of the transit, courtesy of a NASA web site.
Source: NASA; Fred Espenak, Observer's Handbook 2012, Royal Astronomical Society of Canada
View the live stream from NASA, from Mauna Kea, Hawaii.
http://sunearthday.nasa.gov/webcasts/nasaedge/
Here are some other sites that are webcasting the transit live:
Go to a live event near you:
http://sunearthday.nasa.gov/2012/transit/event_locations.php
You can also view the transit directly, but follow these very important guidelines:
"This is a good summary of what a transit is and it uses the recent transit of Venus (June, 2012) as an example."