NCEP Daily Weather Maps 2003 to Present Iowa Daily Summaries Satellite Imagery >> UCAR site
NCEP Maps Back to 1871 HPC Surface Analysis Archive SSEC Ohio State (30 days)
NCEP Reanalysis Plotter Plymouth State (lots of stuff, including blank maps!!!!) NCDC (global, full disk; back to 1983)
NCEP/NCAR Reanalysis Data Composites NOAA CLASS
FSU/CUDOS Raob Site Unidata Master Station List (searchable) NOAA (haven’t explored)
FSL's Radiosonde Archive NCDC - Climatic Extremes and Weather Events METAR and misc
Recent Raobs in Table Format ACARS Data ISU site
Raobs in Table Format back thru 1995 AWESOME SITE: IEM Daily Features
Integrated Global Radiosonde Archive
Radar Reflectivity Archive Gilbert's Archive of METARs, UPAs, etc.
Stage IV Long Term Archive Surface Observations by State (Univ. of Wyoming)
NCDC Weather and Climate Data Unisys Archive
NCDC Digital Data Sets Florida State University's Archive