Nuts, I get so overwhelmed with stuff to do that some important notices get blown off. Like, for example, the fact that the European lunar probe SMART-1 will impact the Moon at 10:41 Pacific time (05:41 Greenwich time) tonight! This probe has been orbiting the Moon since November 2004, taking great data of our nearest astronomical neighbor.
As the mission wound down, the decision was made to have it smack into the Moon so that it will raise a plume of dust and other stuff, so that astronomers back here on Earth can investigate it. The flash from the impact will be faint, almost certainly too faint to see with your unaided eye, but a telescope might make it visible.
For updates, check out The Planetary Society's website. And if you see anything, report it here!