EconModel
This site, run by William R. Parke of UNC Chapel Hill, lets students
and others run simulations of standard micro and macro models. To run
the simulations, you must first download a Windows program. Currently,
all models have a free 10-day trial period. Below is a list of the
available models. As one can see, they cover a fair amount of
undergraduate theory.
Supply and Demand
Who Pays a Sales Tax?
Cobweb Model
Perfect Competition
Monopoly
Price Discrimination
Demand for Labor
Two Goods - Two Prices
Labor Supply
Intertemporal Substitution
The Classical Model
Simple Keynesian Model
IS/LM Model
Mundell-Fleming Model
Real Business Cycles
IS/MP Model
Besides the above, the site also has interesting views of data, such
as the yield curve from the 1950s to today and an animated Phillips
Curve, as well as commentary on current issues.
http://www.econmodel.com/