Educational Math Software

What is the the most educational software for high school and college math?

Not the one that just gives you the answer, but has any of the following:

Edit: Software mentioned in answer added in brackets

    • provides step-by-step solutions [WolframAlpha];
    • can verify your step-by-step solution [empty];
    • can give you hints [empty];
    • can generate problems similar to given one [empty];

    or something along those lines.


    Wolfram Alpha. Try, for instance "solve x^2-x-1=0" and click "show steps".


    Maple can give step-by-step solutions as well as give hints on what rule you could apply next.