<ItemsControl HorizontalAlignment="Stretch" ItemsSource="{Binding Path=...}">
  <ItemsControl.ItemsPanel>
    <ItemsPanelTemplate>
      <VirtualizingStackPanel Orientation="Horizontal" IsItemsHost="True"/>
    </ItemsPanelTemplate>
  </ItemsControl.ItemsPanel>
  <ItemsControl.ItemTemplate>
    <DataTemplate>
      <StackPanel MinWidth="40">
        ............
      </StackPanel>
  </ItemsControl.ItemTemplate>
</ItemsControl>