It's not usual to me, but today I will recommend a tool from ... Microsoft
If you sometimes have got to help the kids to learn a lesson or do their homeworks, and forgot everything you learnt at school to become a P&L manager, a sales manager or an IT manager (who basically now knows only the 4 basic operations : + - x / and forgot everything else), then Microsoft can help you today.
They have released, for free Mathematics 4.0.
It's a graphing calculator. You can plot 2D or 3D lines, you can solve equations and benefot from many other tools that are useful for the one having to deal with Science and Math at work or at school.
x^2 + y^2 + z^1 = 1, in analytic geometry, is the equation true for all points of a sphere of center (0,0,0) and of radius 1.
You just have to enter the equation and click "graph" to see the nice graph appears.
PS : this is not for your office computer except if you still have to deal with science and math ;-)