Google offers web "gadgets," and if you search their gadgets page for "stock chart," you will see a stock chart provided by yahoo. You can size the chart to your desired size and feed it your companies stock symbol, then click the "get code" button which it will give you the JS. I simply added a new row into the HTML of my template I am using and pasted the JS into that row. Only negative is that there is a small "GOOGLE gadgets powered by google" advertisement written beneath the graph. I had to do some other HTML formatting to get the WP to look like I wanted it to, but it works well.
Chad