On 17 March 2013, NASA cameras captured the brightest impact on the Moon seen in eight years of monitoring. It lasted only a fraction of a second, but at the brightness of a fourth-magnitude star it could have been seen by anyone with binoculars and possibly with the naked eye. Six of the 17 frames are shown here. NASA calculates that a boulder 30 to 40 centimeters across, traveling at 25 kilometers per second, was responsible.
On Earth this boulder wouldn't have made it to the ground; pressure and thermal shock would have shattered it high in the atmosphere and it would have been thoroughly atomized. But on the airless Moon it probably left a crater estimated to be 20 meters across. That's big enough for the Lunar Reconnaissance orbiter to spot it the next time time it flies over the spot.
The Moon impact monitoring program has documented about 300 impacts since 2005. It's important to know the statistics of impacts for planning long stays on the Moon. See the whole video, plus more detail and a NASA ScenceCast video over at the NASA Science site.