Plotly is an online service for plotting and analyzing data. It has many different analysis tools and quality environment for creating and presenting high-quality data plots. It requires an account and limits the number of plots that can be created privately, however if you are willing to share your data you can create numerous graphs for free. It is interactive with a number of other programming languages, including [Python], [MATLAB].
Plotly is free to use, however you must create an account and there is a limit to the amount of private data you can use.
Basic instructions are available at http://help.plot.ly/