The Wolfram|Alpha blog has published some information on plotting functions with Wolfram|Alpha. The plots come out quite nice whether 2D, 3D, or contour, and you don’t need to install any software to do some quick plots.

Plotting Functions and Graphs in Wolfram|AlphaMay 17, 2011Plotting functions in the Cartesian plane is such a simple task with Wolfram|Alpha: just enter the function you are looking to graph, and within seconds you will have a beautiful result. If you are feeling daring, enter a multivariate function, and the result will be a 3D Cartesian graph. Wolfram|Alpha is certainly not limited to Cartesian plotting; we have the functionality to make number lines, 2D and 3D polar plots, 2D and 3D parametric plots, 2D and 3D contour plots, implicit plots, log plots, log-linear plots, matrix plots, surface of revolution plots, region plots, list plots, pie charts, histograms, and more. Furthermore, in Wolfram|Alpha we can generate specialized plots for illustrating asymptotes, cusps, maxima, minima, inflection points, saddle points, solutions of ordinary differential equations, poles, eigenvalues, series expansions, definite integrals, 2D inequalities, interpolating polynomials, least-squares best fits, and more. Let’s take a look at the plotting functionality in Wolfram|Alpha, some of which is newly improved!We will start simple with 2D Cartesian plots.

via Wolfram|Alpha Blog : Plotting Functions and Graphs in Wolfram|Alpha.