Great website overall severe weather information such as daily convective outlooks, source for mesoscale discussions, along with mesoscale analysis
I primarily use this website for weather models including the GFS, CFS, Euro, UKMET, GDPS, NAM, NAM 3k, HRRR, RAP, NBM, several versions of the WRF, and ensembles.
Has weather models, but I primarily use this website for satellite data.
Has options to create plots of any imaginable weather or climate product along with a large amount of GIS data.