National USA radar image, map. Updates twice per hour. Links to other radar maps: Summary, Regional, Local NexRad, Storm Relative Mean Radial Velocity.

NEXRAD images directly from the National Weather Service covering the United States.

Extensive meteorological statistics, summaries, and forecasts. Also offers web cam views, interactive maps, historical weather events, archived data, and tutorials.

InterRAD Internet based doppler radar service, GPS based NEXRAD, advanced software since 1994.

The WeatherMatrix organization, formerly CASI, has put together a nice collection of radar-related links. The links range from those to current radar data, to links about radar sites and how they work. StormMatrix, a very unique feature to the Internet, is the only place you can find free NEXRAD storm table data online(30 min delay).

Commercial site offering NexRad Doppler Radar maps, updated every 6 minutes, including national, regional and state radar maps, and lightning strike data.