There is a recently discovered comet which is rounding the sun even as we speak. This is a cool enough event in and of itself, but its coolness factor is enhanced about 1000% by dint of the fact that you can observe it in near-realtime online.
The Solar Heliospheric Observatory (SOHO) watches the Sun 24/7, returning images of amazing quality and quantity, and you can see them anytime at
http://sohowww.nascom.nasa.gov/ . There is a link to videos dedicated to this comet passage (check out the Lasco C3 images for the best views). This link will take you directly to the most recent images and image sequences.
http://sohowww.nascom.nasa.gov/data/...me-images.html