Here is a list of observatories and organizations providing live webcasts on June 5 of the Venus transit of 2012:
NASA webcast from Mauna Kea, Hawaii: http://venustransit.nasa.gov/2012/transit/webcast.php
Exploratorium (in San Francisco, Calif.) webcast from Mauna Loa, Hawaii: http://www.exploratorium.edu/venus/
Slooh Space Camera telescope feed from around the world: http://www.slooh.com/transit-of-venus/
Astronomers Without Borders webcast from the Mount Wilson Observatory in California: http://www.astronomerswithoutborders.org/projects/transit-of-venus.html
I intend to publish a single list later.