If you're really desperate for entertainment, the spreadsheet I use in class that makes graphs with the income-expenditure model can be found at:

    Uwbunsec
          Magenta
              Public
                 Danby's 324

You can make a copy and try changing the values of I, G, T, and so forth.

Unfortunately I can't automatically generate those little plumbing diagrams of macro flows for different model results.  Does anyone know how to do that?