Right this very minute, Mercury—that’s the baby planet closest to the sun—is passing between the sun and the Earth. This will next happen in 13 years, and this one ends at 1:45 p.m. ET, so right now is your chance to see it.
Mercury is too small to see with your bare eye, so unless you have access to a fancy telescope with special filters, you can visit Slooh, the robotic telescope service, which is live-streaming it here, along with ongoing commentary from astronomers and scientists.
Also, the good people at NASA are using our tax dollars brilliantly, to provide us with these small video files of Mercury moving across the face of the sun.