If you’ve got some math functions that need plotting, you can do it pretty easily with Function Plotter, available as both a Windows 8 app and Windows Phone 8 app.
Besides looking great, the app also gives you useful at-a-glance information automatically, such as maximum and minimum points, derivatives, antiderivatives, intersection points with a second function, integrals, and more. For those taking math courses or just needing to do some basic function plotting, Function Plotter makes it both easy and visually appealing.
Do beware, however, that there seems to be a range limit on the X and Y axis that can be displayed in the graph. I couldn’t seem to get the X-axis range to go past [-40,40], while the Y-aixs was able to go a little further to [-49.06,49.06]. I do wish the range options were more customizable, as currently you can only pick from a set list of symmetric ranges, so you can’t just view the positive X and Y quadrant, for example.
I would recommend using Function Plotter for quick plotting of functions with a beautiful interface.