An football-field-sized asteroid has been discovered that this weekend will sort of pass near the earth (actually, 2.5 times the distance from the earth to the moon, so not all that close). The neat thing is that it was discovered a week before it reaches a spot closest to earth. See this (h/t Wendy).
Finding this asteroid a week before it flies by us is close to the goal of astronomers that are in the process of building early warning systems, but they want to get a week's advanced warning for objects half the size of 2013 ET, and probably up to 2 weeks for something of its size.