How do I dynamically bind and statically add MenuItems?

You can use a CompositeCollection to do this, you can combine different Collections and add static items in the xaml.

Example:

Xaml:

<Window x:Class="WpfApplication8.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="233" Width="143" Name="UI">
    <Window.Resources>
        <CollectionViewSource Source="{Binding ElementName=UI, Path=Windows}" x:Key="YourMenuItems"/>
     </Window.Resources>

    <Grid DataContext="{Binding ElementName=UI}">
        <Menu Height="24" VerticalAlignment="Top">
            <MenuItem Header="_View" >
                <MenuItem Header="Windows">
                    <MenuItem.ItemsSource>
                        <CompositeCollection>
                            <CollectionContainer Collection="{Binding Source={StaticResource YourMenuItems}}" />
                            <MenuItem Header="Menu Item 1" />
                            <MenuItem Header="Menu Item 2" />
                            <MenuItem Header="Menu Item 3" />
                        </CompositeCollection>
                    </MenuItem.ItemsSource>
                    <MenuItem.ItemContainerStyle>
                        <Style>
                            <Setter Property="MenuItem.Header" Value="{Binding Title}"/>
                        </Style>
                    </MenuItem.ItemContainerStyle>
                </MenuItem>
            </MenuItem>
        </Menu>
    </Grid>
</Window>

Code

public partial class MainWindow : Window
{
    private ObservableCollection<MyObject> _windows = new ObservableCollection<MyObject>();

    public MainWindow()
    {
        InitializeComponent();
        Windows.Add(new MyObject { Title = "Collection Item 1" });
        Windows.Add(new MyObject { Title = "Collection Item 2" });
    }

    public ObservableCollection<MyObject> Windows
    {
        get { return _windows; }
        set { _windows = value; }
    }
}

public class MyObject
{
    public string Title { get; set; }
}

Result: