The transit of Venus across the sun is coming up on June 5th! If you would like to go to a viewing event in your area, NASA has setup a handy map for you to locate an event. For ham radio operators, there are plans to collect transit data via APRS.
For everyone that's interested, you can learn more at the following links:
NASA school workbook on the mathematics of the transit [pdf]
The workbook doesn't have an explanation of parallax measurements. It turns out that Parallax is more than just a comic book character. It's the process by which you can calculate the distance from the earth to the sun using transit data. Wikipedia however, has a great page on parallax.
Finally, there is a smart phone app for recording transit data. Picture of the Day