Dynamics
MIT tropopause maps ("most functional" award).
UW tropopause maps ("prettiest maps" award).
Albany maps ("most customizable" award).

Regional Model Forecasts
National Weather Service GFS-LAMP forecasts.
COLA forecasts & data (more stuff).

Data
National Weather Service CONUS radar loop (enormous .gif -- hope you have a 30" monitor).
GOES imagery.
SSMI -- assimilated radiometer, surface winds, SST, P-E, etc...
TAO -- tropical Pacific observations.
ECCO -- Estimating the Circulation & Climate of the Ocean.
U. Wisc. SSEC -- Realtime imagery.

Fast & Easy
geoipweather
NWS Enhanced Data Display

Misc.
Cloud atlas.
ICAT Damage Estimator