The odetoolkit lets you enter a first order ode or system in normal form and then solve the initial value problem numerically, presenting the results either graphically or in tabular form. The solvers are based on the LSODA and CVODE packages. Advantages: Fairly easy to use. A number of prepared examples are available in the library. The system supports a number of functions that are unusual in purely mathematical packages but useful in engineering (e.g. square waves). It is possible to enter equations with parameters that can be updated on their own lines making it easy to see how changing the parameter changes the results. Disadvantages: The library examples could use better documentation on where the model equations come from. The system is somewhat picky about how equations are entered and error messages just say see the documentation. Only initial value problems are allowed and higher order equations must be converted to first order systems. The documentation "assumes the reader is somewhat familiar with numerical methods."