Today, 6/14/12, A asteroid the size of a city block will fly by the earth.
The astrtoid is named 2012 LZ1. Astrinomers estimate it is about 1,650 feet, or 500 meters wide. It is going to come within 14 lunar distances of the earth tonight. There is no danger of an impact, but you might be able to get the asteroid on camera.
You will be able to watch it online though the skywatching service, they will have a telescope on the canary island watching 2012 LZ1 and be streaming footage live. They will start the live feed at 8:00 p.m. EDT, this is the time of closest approach.
Astronomer Rob McNaught, is the asteroids finder, and he will participating in the live feed, along with Astronomy magazine columnist Bob Berman.
Asteroid 2012 LZ1 captured from an Italian Observatory
You can watch it live on http://events.slooh.com/