An example spreadsheet for this is available in HTML or XML. This was made based on the fantastic JSON spreadsheet example from Google and the dynamic charting example from PlotKit. It follows that this uses the Plotkit charting library & Google Spreadsheets API.
To find the spreadsheet and worksheet ID for your Google spreadsheet:
Click "Load Worksheet Data" button when done. If your worksheet loaded successfully & you're using Firefox, you'll see a snapshot of the column data below. Note that the first row is treated as the header row - so it's best to put descriptive column titles there (e.g. "year", "revenue").