Apollos, Atens, and Amors are the NEA families currently known, with about 500 known I think, plus another 1700+ which are still having their orbits analyzed. It is likely that one of these families of NEAs struck the Earth 65 million years ago, extinctifying (I just coined that) the dinos. Given the number of potential encounters, probably all, or nearly all, the catastrophic impacts (such as the one that formed the Ries Basin in Germany, the Haughton astrobleme in the Canadian Arctic, the Tunguska event) result from encounters with these NEAs.
Near-Earth Asteroid Tracking
http://neat.jpl.nasa.gov/
Binary Near-Earth Asteroids
http://www.asu.cas.cz/~asteroid/binneas.htm
Current Map Of The Solar System
http://szyzyg.arm.ac.uk/~spm/neo_map.html