The best place to find charting examples would be at the Silverlight Toolkit Codeplex. There you can find all kind of interactive samples with code.Here is a simple pie chart example:
<!-- Typical Use -->
<Grid Style="{StaticResource WrapperStyle}">
<chartingToolkit:Chart Title="Typical Use">
<chartingToolkit:Chart.Series>
<chartingToolkit:PieSeries ItemsSource="{Binding PugetSound, Source={StaticResource City}}" IndependentValueBinding="{Binding Name}" DependentValueBinding="{Binding Population}"/>
</chartingToolkit:Chart.Series>
</chartingToolkit:Chart>
</Grid>
Where ChartingToolkit refers to:
xmlns:chartingToolkit="clr-namespace:System.Windows.Controls.DataVisualization.Charting;assembly=System.Windows.Controls.DataVisualization.Toolkit"
Hope this helps.