The lyrics of  "King of Pain", by Sting & Police starts like this:
  There's a little black spot on the sun today
  It's the same old thing as yesterday
But today there is a different little black spot on the sun!  It's 
the planet Mercury passing between the Sun and the Earth!!
Today, November 8, the planet Mercury passes inferior conjunction 
with the Sun, where it is in between the Sun and Earth. Because of 
the tilt of the planetary orbit, Mercury is usually not QUITE 
aligned, but passes either above or below the solar disk.  This time, 
however, the planet passes right across the Sun for a "transit." 
Transit seasons are early November and May. November events are 
separated by intervals of 7 or 14 years.  May transits (which take 
place with the planet farther from the Sun) are rarer, and can, but 
don't have to, recur in 14 years. (Transits of Venus are far rarer. 
There were none in the twentieth century; the last one was in 2004, 
the next in 2012.)
Unfortunately, Transits of Mercury are NOT visible to the naked eye, 
even with appropriate
filters, but are readily visible with the telescope.  However, they 
should be viewed by projection only; do not even try without 
professional-level knowledge or help.  The event begins at 1:12 PM
CST (2:12 EST, 12:12 MST, 11:12 AM PST, 9:12 AM Hawaii), and lasts 
for about 5 hours as the planet slowly moves in orbit.  Only the 
western US and Canada will witness the whole thing before sunset. The 
timings of such transits were once used in attempts to local times 
and thus longitudes. This description courtesy of Jim Kaler: 
http://www.astro.uiuc.edu/~kaler/skylights.html
Since this is a telescopic event, and then only through solar safe 
telescopes, I thought I'd provide our OTAstronuts with a virtual 
viewing of the transit.  I'll be here at JPL, with three solar-safe 
telescopes, Mojo is at work with one additional safe telescope, and 
our frequent sidewalk astronomy telescope operators Gary and his 
daughter Elizabeth are setting up a solar safe telescope at 
Elizabeth's school today.
So sit back, and use these links.  The transit begins at 11:10 a.m. 
here on the west coast and ends at 4:10 p.m. If you miss this one, 
don't worry, it'll happen again in 2016!
APOD (Astro Photo Of the Day) - simulated transit of Mercury 
http://antwrp.gsfc.nasa.gov/apod/
A nice animation and description 
http://science.nasa.gov/headlines/y2006/20oct_transitofmercury.htm
A webcast - one of many, you can  probably find others if this is 
busy using your favorite search engine: 
http://www.exploratorium.edu/transit/
A nice visual description, shows size of Mercury  - looks fine on the 
screen, white text doesn't show up on printed copies: 
http://www.exploratorium.edu/transit/what.html
I am using this handout: 
http://sunearth.gsfc.nasa.gov/eclipse/OH/tran/TM2006sun.GIF
Todays sunspots here - the sunspot image also shows size of Earth and 
Jupiter for a great size explanation.  :-) 
http://sohowww.nascom.nasa.gov/
Finally, this transit is not visible everywhere on Earth. The transit 
will be widely visible from the Americas, the Pacific Ocean, eastern 
Asia, and Australia
US map here 
http://sunearth.gsfc.nasa.gov/eclipse/OH/tran/TM2006map.GIF
Global view here 
http://sunearth.gsfc.nasa.gov/eclipse/OH/image1/TM2006Nov08-Fig2.GIF
Jane
-- 
Jane Houston Jones
Senior Outreach Specialist, Cassini Program
JPL - 4800 Oak Grove Drive, MS 230-205
Pasadena, CA  91109  818-393-6435
jane.h.jones(a)jpl.nasa.gov
Cassini Saturn Observation Campaign
http://soc.jpl.nasa.gov/index.cfm