Plotting & Graphics
A few examples of what you can ask Wolfram|Alpha about:
plot a function of one variable
specify an explicit range for the variable
plot a function where it is real-valued
plot a special function
plot several functions
plot a function on a logarithmic scale
plot on a log-linear scale
3D Plots
plot a function of two variables
specify explicit ranges for the variables
plot the solution to an equation in two variables
plot a quadric surface
plot the region satisfying an inequality in two variables
plot a region satisfying multiple inequalities
Polar Plots
draw a polar plot
specify a range for the variable theta
Parametric Plots
draw a parametric plot
specify a range for the parameter
visualize a set of real numbers on a number line
show multiple sets on a number line