If you construct graphs a lot, you may want to check out some great online graphing tools listed below.
1.) Desmos Calculator and Grapher is an excellent online graphing tool that can plot points, graph parabolas, conic sections, and even Fourier expansions. Aside from being a grapher, it is also an online calculator.
2.) Graph.tk is one of the easiest to use online grapher. It can graph a wide variety of functions including derivatives, absolute value functions, and polar graphs.
3.) Graph Sketch. Graph Sketch is an online graphing software created by Andy Schmitz. It is capable of graphing standard and parametric functions. Graph results can either be downloaded or save as page that you can linked to.
4.) Rational Function Plotter. Rational function plotter allows you to plot rational functions. The applet allows you to specify the domain, range, and other properties of graphs such as thickness, gridlines, tick marks, etc.
5.) Function Grapher and Calculator. Function Grapher and Calculator is another tool for graphing functions. Unlike other sites, it is easier to zoom in Equation Grapher.
6.) Wolfram Alpha. Wolfram Alpha not only plot graphs but also computes for the critical points of graphs such as its local maximum, minimum, roots, etc. Wolfram Alpha can do a lot more than those. To know more about it, click here.
7.) GeoGebra. GeoGebra has an online version which can be used for Graphing. called the Applet Start. Its basically the identical version of GeoGebra.
8.) Holt Online Graphing Calculator. The Holt graphing calculator can graph up to four functions at a time. Aside from the graph, HOGC also provides a table of integral values.
9. Fooplot. This is another good function plotter. You can plot up to four functions. The output can saved in eps, png, pdf, and svg format.
If you know any good online graphing software, please inform me so we can include it in the list.