- Mathtools (This is a technical computing portal for all scientific and engineering needs).
     - Wolfram (makers of MATHEMATICA)
    - MathWorks (makers of MATLAB)
    - Waterloo Maple (makers of MAPLE)
    - MathSoft (makers of MATHCAD and S-PLUS)
    - Macsyma (makers of MACSYMA)
    - Numerical Objects
    - Leibniz (Graphical MATHEMATICA front end)
    

Specific to modeling or biological applications

    - XPP for Window 98/NT(a nice de solver, including some delay des) 
    - Software for delay differential equations
    - ECOTOOLS
    - PISCES conservation