Near Earth Objects (NEOs) are plentifull.

Asteroid hit.: Artist: Don DavisIf a person lives to be 80, her or his odds of being around when the next multi-megaton blast from an asteroid collision occurs (somewhere on the planet) are roughly 1 in 12.5. Space within Earth's orbit is crowded with Near Earth Objects. Here is a link to a video of the movement of hundreds of NEO's (400 days).

Some recent near misses

• On March 18, 2004, Asteroid 2004 FH passed approximately 26,500 miles above the Earth's surface (one-tenth of the distance to the Moon). Astronomers had detected it just three days before.
• Another near earth object designated 2004 AS1 created concern on Jan 13, 2004. Initial measurements indicated that it would hit Earth within 27 hours. "Astronomers come within minutes of alerting the world to a possible asteroid strike." Wired News
• Near Earth Asteroid 2004 MN4, briefly held a Torino Scale index of 4 (a record high) before being declared safe.

Near miss: Asteroid 2004 FH's flyby (NASA/JPL)

More Near Earth Object links

NASA impact risk assessment FAQ.
Armagh Observatory information.
NASA NEO basics. page
NASA images.