Daily Weather Maps for the Continental US.
NCEP National Center for Environmental Prediction. Make your own meteorological maps of geopotential heights, precip, solar radiation, etc.
Hysplit air trajectory analysis. Forecast as well as archived data.
Storm Prediction Center analysis. Forecast as well as archived data.
Earth School Winds and Meteorology.
Click on the three horizontal bars on the lower left to choose the data you want to see, and " Control:Choose date" for archived data. Zoom to see details.
Archived Radar and GOES Satellite Imagery NOAA Weather and Climate Toolkit (download program and run it from your computer to acquire and visualize data).
Composite radar data for the US or specific radars.
Archived Meteorological Data and Model selected surface, radar, and 500 mb level model.
NASA Worldview satellite imagery with many add on layers.