Sten Odenwald of NASA Goddard Space Flight Center put together these FAQs at http://image.gsfc.nasa.gov/poetry/venus/TransitFAQs.html:

Why do transits happen?
How often do they happen?
How many transits have been observed by humans?
What is a Black Drop?
Why were scientists so excited by transits of Venus?
Who discovered the atmosphere of Venus?
What is an Astronomical Unit?
Who observed the first transit?
Why did John Philip Sousa write the Transit of Venus March in 1883?
How long does a transit of Venus last?
Are astronomers still interested in the transit of Venus?
Could ancient Chinese sunspot observers have seen a transit of Venus?
Why did Kepler not know about the 1639 transit?
How was the transit used to determine the distance from Earth to the Sun?