Phil Plait at Bad Astronomy Blog has posted his top ten images post for the year as well.
My favorite is above- I do love me some lightning. Here's the explanation:
Jens Hackmann took this stunning picture of a lightning storm near the Weikerscheim Observatory; the 300 second exposure is enough to see the stars streak and the observatory lit up by ambient light. Sometimes, when it’s cloudy, observing is difficult… but you can still get incredible pictures.I agree with Plait, astronomy IS the most lovely science.