On the Sony AK Knowledge Center there's a new tutorial showing how to use FusionCharts (Free) to create a real-time charts with no page refresh. FusionCharts is an open source Flash charting component for desktop and web apps.

We will create realtime chart data update that reflect to price fluctuation. There is a line type chart to visualize the price fluctuation. The data of price fluctuation will be fetched from database every 5 seconds using Ajax call and then display the latest 5 (five) data to the chart without any page refresh.

Using FusionCharts and Prototype, they show how to pull information out of a backend MySQL database into a basic graph (HTML and Javascript provided) with a periodic update that grabs the latest from the backend PHP script and pushes it to the graph. You can see an example of the graph here.