If you need plotting capabilities but the current computer where you are in does not have Jmol or Molekel installed, you can run JSmol, a javascript version of Jmol from our website. Just go to the Utilities tab in the top menu and select "General Jmol Viewer". It will load a sample molecule by default.
In the graphics area, you can click the right-hand side mouse button and goto File->Load->Open local file to open a file from your computer, it works with the files we usually handle in the lab (.xyz, .cube, .MOLDEN).
If you need special plotting functions, for now you can use the provided console by selecting "Console" (again with the righ-hand side mouse button). If you need the commands to plot wavefunctions with the console check this article (we're currently working on getting this functionality through buttons).
In order to save files to you local computer select File->Export->Export POV-ray image. This will download the .pov and .pov.ini files for your currently displayed image, you can also download to .png or .jpg formats but .pov is configurable as it is not a graphic image yet, for an example of this check here.