US Forecasts 

Short-range (up to 3 days):

GFS(Global Forecasting System) (ex AVN)- global 
ETA (Eta coordinate Model) - regional
NGM (Nested Grid Model) - regional

Medium range (up to 10days):

GFSX (Global Forecasting System Xtended) (ex MRF) global
ECMWF (European Centre Medium Range Weather Forecast) - global

Useful links:

NWS-Numerical Models
EMC (Environmental Modeling Center) Model Info
NCAR (RAP) Forecast Page 

Time-Height Cross Sections

Ensemble Forecasting