How to disable highlighting on listbox but keep selection?

Late answer, but there's a much better and simpler solution:

<ListBox>
   <ListBox.Resources>
      <SolidColorBrush x:Key="{x:Static SystemColors.HighlightBrushKey}" Color="Transparent" />
      <SolidColorBrush x:Key="{x:Static SystemColors.HighlightTextBrushKey}" Color="Black" />
      <SolidColorBrush x:Key="{x:Static SystemColors.ControlBrushKey}" Color="Transparent" />  
   </ListBox.Resources>
</ListBox>

This allows you to have a LisBox that looks just like an itemscontrol, but has support for selection.

Edit: How it works
This alters "colors of the system", in other words your windows theme, only for this ListBox and its children (we actually want to target the ListboxItem).

For example hovering a ListboxItem usually gives it a deep blue background, but here we set it to transparent (HighlightBrushKey).

Edit (30 June 2016):
It seems for latest Windows version this is not enough anymore, you also need to redefine InactiveSelectionHighlightBrushKey

<SolidColorBrush x:Key="{x:Static SystemColors.InactiveSelectionHighlightBrushKey}" Color="Transparent" />

Thanks to @packoman in the comments

        <ListBox.ItemContainerStyle>
            <Style TargetType="ListBoxItem">
                <Setter Property="IsSelected" Value="{Binding Content.IsSelected, Mode=TwoWay, RelativeSource={RelativeSource Self}}"/>
                <Setter Property="Template">
                    <Setter.Value>
                        <ControlTemplate TargetType="ListBoxItem">
                            <ContentPresenter/>
                        </ControlTemplate>
                    </Setter.Value>
                </Setter>
            </Style>
        </ListBox.ItemContainerStyle>