While I usually put these in a Canvas module for students, sometimes it's easier not to log into anything and just point and click. Here are the basic forecasting links I use.
Wx Challenge
MOS for WxChallenge site (change the URL for current station & Allow pop-ups)
Forecast Discussions to Read
BoulderCast (this usually won't load on campus)
Surface Observations
Surface Observations (click on DEN)
MSU Denver campus weather station (scroll down)
NWS Current obs for Denver (and access to 3 Day History)
CoCoRaHS (great for precipitation observations including snow)
Surface Observations on US map (click to zoom) with frontal locations
Soundings from University of Wyoming archive (Choose Type of Plot-->GIF: Skew-T, then click on station on map)
Radar (U.S. from University of Wisconsin)
Forecast
Severe Weather
Fire and Air Quality or Smoke
Floods
Tropical Cyclones (Hurricanes, Typhoons, Cyclones)
CIMMS Tropical Cyclones Group (click on the storm of interest on the map to get started)
Climate