Xfunctions. Graphs functions, ODE's and more. Fast learning curve.
PhasePlane microscope. This also allows you to watch the evolution of sets of intitial conditions.
Mac software
Mathpad, my favorite, lightweight calculator (from Mark Widholm at U. of New Hampshire)
3d filmstrip, by R. Palais at Brandeis University. This application is designed for graphing surfaces and ODE's for classroom use. It has unique features not duplicated, even by Mathematica, Maple or MatLab.
