Widgenie is a great new (beta) site for creating graphs/charts. It is very similar to Lovely Charts or Rich Chart Live. While I think the latter are both great sites, Widgenie happens to be my favorite because it is very user friendly and creates some very nice looking graphs. (RCL is a close close second).
What makes Widgenie such an attractive option for education is the ability to upload any: Excel, csv, Google Spreadsheet, etc file. This pretty much covers the gambit for any spreadsheet. Also, once the file is uploaded you can edit it to get the exact look/feel you want. For example, you can choose an animated pie chart, bar graph, or even text cloud. Plus, you can edit all the fields via the drag/drop user interface. This really is ideal for the average user.
Finally, once you are finished w/ your graph you can create a link, which lets users share your embed code, or you can just embed it into your own site.
Below is an example I made for a "Heat" graph...
Give it a try by clicking here.