<UserControl.Resources>
    <ItemsPanelTemplate x:Key="ItemsPanelTemplate1">
        <Intersoft:UXStackPanel Orientation="Vertical" AllowMoveItem="True" AllowDropItem="True" AllowReorderItem="True" AllowRemoveItem="True"/>
    </ItemsPanelTemplate>  
</UserControl.Resources>

<Grid x:Name="LayoutRoot" Background="White" DataContext="{Binding Source={StaticResource SampleDataSource}}">
    <StackPanel HorizontalAlignment="Left" VerticalAlignment="Center" Width="250">
        <ListBox x:Name="ListBox1" ItemsPanel="{StaticResource ItemsPanelTemplate1}">
            <ListBoxItem Content="To-do: Prepare Walkthrough Materials"/>
            <ListBoxItem Content="To-do: Prepare Video Materials"/>
            <ListBoxItem Content="To-do: Create Press Release"/>
        </ListBox>
        <Intersoft:FieldLabel Header="Selected Index: " HeaderWidth="100" HorizontalHeaderAlignment="Right">
            <TextBlock Text="{Binding SelectedIndex, ElementName=ListBox1}" VerticalAlignment="Center"/>
        </Intersoft:FieldLabel>
        <Intersoft:FieldLabel Header="Selected Item: " HeaderWidth="100" HorizontalHeaderAlignment="Right">
            <TextBlock Text="{Binding SelectedItem.Content, ElementName=ListBox1}" VerticalAlignment="Center"/>
        </Intersoft:FieldLabel>
    </StackPanel>
    <ListBox x:Name="ListBox2" ItemsPanel="{StaticResource ItemsPanelTemplate1}" HorizontalAlignment="Right" VerticalAlignment="Center" Width="250" 
                                ItemsSource="{Binding Collection}" DisplayMemberPath="Property1"/>        
</Grid>

public MainPage()
{
    // Required to initialize variables
    InitializeComponent();

    ISEventManager.RegisterInstanceHandler(
        this.ListBox1, // any element in the routed path which applicable in your scenario
        DragDrop.DropEvent, // the routed event
        new Intersoft.Client.UI.Controls.Interactivity.DragEventHandler(DropTarget_Drop), // the event handler
        true);
}

private void DropTarget_Drop(object sender, Intersoft.Client.UI.Controls.Interactivity.DragEventArgs e)
{
    ListBoxItem dropElement = e.GetDropElements()[0] as ListBoxItem; // get the drop element
    Expression.Blend.SampleData.SampleDataSource.Item dataContext = dropElement.DataContext as Expression.Blend.SampleData.SampleDataSource.Item; // get the data context
    dropElement.Content = dataContext.Property1; // set the content
    dropElement.ContentTemplate = null; // clear the content template from previous bound ListBox.
    dropElement.DataContext = null; // clear the data context if necessary.           
}