The "Science" of Hollywood
http://www.skypub.com/news/special/impact/hollywood.html

Send an asteroid or comet hurtling toward your favorite planet- Calculator!
http://janus.astro.umd.edu/astro/impact.html

Meteorite Homepage- (a Ton of info)
http://seds.lpl.arizona.edu/nineplanets/nineplanets/meteorites.html

Impact craters
http://www.sciam.com/askexpert...

Asteroid Impact Probability
http://www.sciam.com/askexpert...

Dino Impact
http://www.stsci.edu/exined/Impact.html

Impact of asteroid off NYC coast
http://sherpa.sandia.gov/planet-impact/asteroid/

SpaceWatch Project
http://www.skypub.com/news/special/impact/spacewatch.html
http://www.lpl.Arizona.edu/spacewatch/

The NEO Page
http://cfa-www.harvard.edu/iau/NEO/TheNEOPage.html

The SpaceGuard Foundation
http://cfa-www.harvard.edu/~marsden/SGF/

Near Earth Objects Dynamic Site
http://newton.dm.unipi.it/neodys/

Minimum Orbital Intersection Distance (definition & table)
http://www.lowell.edu/users/elgb/moid.html

Scientific Technical Foundation
http://www.snezhinsk.ru/asteroids/eng/ssf/

TASS, The Amateur Sky Survey
http://www.tass-survey.org/tass/tass.shtml

Terrestrial Impact Craters- Nice info and pictures from around the world
http://www.solarviews.com/eng/tercrate.htm

Asteroid Info Page
http://www.solarviews.com/eng/asteroid.htm

NASA Sites

Asteroid Radar Research
http://echo.jpl.nasa.gov/

Deep Space 1- mission to do comet flybys
http://nmp.jpl.nasa.gov/ds1/

Mathilde flyby
http://near.jhuapl.edu/Mathilde/

Minor Planet Center
http://cfa-www.harvard.edu/cfa/ps/mpc.html

Asteroid Observing Services
http://asteroid.lowell.edu/

Real NASA mission "Deep Impact"
http://deepimpact.umd.edu/home/index.html