US Forecasts 

Short-range (up to 3 days):
GFS(Global Forecasting System) (ex AVN)- global 
NAM (North America Mesoscale) - regional

Medium range (up to 10days):
GFSX (Global Forecasting System Xtended) (ex MRF) global
ECMWF (European Centre Medium Range Weather Forecast) - global

Model info:
MetEd:Operational Model matrix
NCEP Model Analyses & Forecasts(pdf)
EMC (Environmental Modeling Center) Model Info
GFS products
NAM products

Useful links:
NCEP "map" view
Time-Height Cross Sections (B. Tang)
Model Output Statistics
NCAR (RAP) Forecast Page 
Probabilistic guidance   SREF Portal