The Transit of Venus
A great site to get started learning about this is http://www.transitofvenus.org/, which is where I found a link to the simulation below. This simulation is centered on Toronto (but you can change it), and it shows that Venus will only be crossing the sun from 18:04 to 20:53.
Remember that it's not safe to look directly at the sun, so if you do want to watch the transit live, visit http://www.transitofvenus.org/june2012/eye-safety to learn some safe techniques.
I've bookmarked a few links related to the Transit of Venus, which you can find here. My list is not comprehensive, so I urge you to explore other sites and see what you can learn!
Will you be watching the transit? Will you be telling your students about it?