Comment on MathPad

This little app is really good for any (numerical) tasks you can't be bothered to program in C or are not worth buying MatLab/Mathematica/etc. It can do simple computations, function definitions, arrays, matrices, nested loops, plot in 2D, 3D (either the traditional way or by creating a color map of the values). It's pretty fast.

And it has sliders for variable parameters: if you define a slider, you get a little window with a scroll bar, and as soon as you move the it, the new value is used and everything is recomputed. So if you've got a plot depending on a couple of parameters, you can easily experiment with different values.

Highly recommended.