Near Earth Objects
The NEO Information Centre is part of the United Kingdom government's response to the Report of the Task Force on Potentially Hazardous Near Earth Objects and provides services to the public, educators, media, and scientists to encourage understanding and advancement of near earth object science.
The U.S. Geological Survey offers this "Themes" page on geomagnetism and geomagnetic storms from the National Geomagnetic Information Center. It includes background information about the center, as well as numerous charts, publications, and other information and tools for studying and monitoring this phenomenon.
The Web site of NOAA's Space Environment Center (SEC) is the "Official Source of Space Weather Alerts, Warnings, and Forecasts." The site provides online data, educational materials about space weather hazards, and descriptions of SEC projects and services. Most notably, it provides a "Space Weather Now" page at the second URL above with information on imminent or ongoing solar radiation storms, geomagnetic storms, and radio blackouts, as well as real-time information about solar and auroral activity. The page also links to separate pages for SEC user groups (navigation, radio, electric power, satellite operators, the media).
This well-designed site prepared by Australian Michael Paine is a treatise on the potential tsunamis generated by asteroids or comet impacts. Besides attractive graphics and animation, the site is well documented and includes links to numerous other scholarly works on this hazard.