The Flash driven line and area chart from amCharts is a great way to display data dynamically on your site. All the data needed are stored in a separate XML file, so updating is done in seconds. You can zoom a selected period just by clicking and dragging, turn on/off each individual graph and all values are shown when hovering. Yet another XML file allows you complete control over every colour, size, font and background.

Short features list:

• can be any size;
• size can be defined in percents – you can have full screen chart;
• Weights only 30 Kb;
• Works even with Adobe Flash Player 7 and higher;
• Loads data from XML or CSV (coma separated values text file), this means you can easily export data from Excel, dynamically generate data file with PHP, ASP, .NET or other programming language;
• ZOOM function!
• possibility to show/hide graphs, especially comfortable if you have a lot of them;
• value indicator;
• handles missing data;
• intelligent minimum and maximum value calculation algorithm;
• can have two Y axes (left and right);
• predefined and custom bullets;
• you can add any number of labels or texts on your chart;
• you can add comments for any of your values;
• possibility easily provide help for your chart users;
• You can use background image - JPG or even animated flash (SWF) background;
• and more…

You can download it for free, however free version will display a small link to their website on your charts. I’m currently using it to display my weekly stats.