Online Function Grapher is an online tool that draws functions specified via a mathematical formula on a two-dimensional chart.
The domain has been online since March 2011; since then the attention to details was managed pretty well: the scrolling wheel on the mouse can be used to zoom in or zoom out the graph, and a lot of expressions are recognized, such as sqrt (square root), x^y (x to the power of y) or sin/cos/tag functions.
The webapp includes additional features, such as saving the current image as a .jpeg, or linking to it for someone else’s benefit.
The tool has enough features to be a powerful aid when it comes to function plotting, but it still manages to keep everything simple by using a clean and powerful interface. While it doesn’t offer advanced features which would make it compete with more advanced tools in this field, it has enough simplicity and intuitiveness of the UI to become a powerful aid when one needs a quick graph or plotting job (or is simply curious how a function really looks like).