The Winter '12 release has a new pilot feature, Visualforce Charting. Visualforce charting is a collection of components that provide a simple and intuitive way to create charts in your Visualforce pages and custom components. Visualforce charting gives you an easy way to create customized business charts, based on data sets that you can create directly from SOQL queries, or by building the data set in your own Apex code.

Here's what a simple chart might look like:

<apex:page controller="PieChartCtlr" title="Pie Chart">
 <apex:chart data="{!pieData}">
   <apex:pieSeries labelField="name" dataField="data1"/>
 </apex:chart>
</apex:page>

The output may look something like this:

Here is a blog post describing this feature in greater detail:

• A Quick Look at Visualforce Charting