I'll try not to make a habit of these but this is a genuine "once in a
lifetime" opportunity (unless you plan to live to be several hundred years
old :-))

NASA Space Science News for November 12, 1999

Look at that Sunspot Go! -- On Monday afternoon, November 15, the
planet Mercury will pass in front of the Sun, creating a speedy dark
spot on our star that can be seen through properly filtered telescopes.
The unusual grazing geometry will not be repeated for centuries.
FULL STORY at

        http://science.nasa.gov/newhome/headlines/ast12nov99_1.htm