At 22:09 UT on June 5, 2012 the planet Venus will appear as a small, dark disk moving across the face of the Sun. The transit will finish at 04:49 UTC on June 6 (exact time depends on location of observer).
Clouds permiting, it may be visible to observers in the UK from dawn (about 03:46 UT in London).
This will be the last time the planet Venus will make the trek across the face of the sun as seen from Earth until the year 2117.
Note: Observing the Sun directly without appropriate protection can damage or destroy retinal cells, causing temporary or permanent blindness.
Clint Bradford K6LCS has posted a collection of URL’s where you should be able to watch the Venus transit online from sites around the world.
NASA (USA) http://venustransit.nasa.gov/2012/transit/
University of Barcelona (from a telescope in Norway) https://gaia.am.ub.es/serviastro/www/html/venus2012/live/index.html
National Solar Observatory http://venustransit.nso.edu/live.html
Exploratorium (via the Mauna Loa Observatory) http://www.exploratorium.edu/venus/
NASA TV http://www.nasa.gov/ntv
Coca Cola Space Science Center (from Australia) http://www.ccssc.org/transit2012.html
Bareket observatory (Israel)
Mt. Lemmon Sky Center http://skycenter.arizona.edu/annoucement/live
Astronomers Without Borders (from Mt. Wilson, California)
The 2012 Transit of Venus using HAM Radio http://aprs.org/VenusTransit2012.html
Transit of Venus Special Event June 6, 2012
Ultra-high Definition video recording of 2012 Venus Transit