Make Label/TextBlock readable on glass using blur effect

    <TextBlock ...>
        <TextBlock.Effect>
            <DropShadowEffect BlurRadius="10" Color="White" ShadowDepth="0" />
        </TextBlock.Effect>
    </TextBlock>

As per Luke's request, I include the XAML for Decorators:

<Decorator>
    <Decorator.Effect>
        <DropShadowEffect BlurRadius="7" Color="White" ShadowDepth="0" />
    </Decorator.Effect>
    <Decorator>
        <Decorator.Effect>
            <DropShadowEffect BlurRadius="7" Color="White" ShadowDepth="0" />
        </Decorator.Effect>
        <Decorator>
            <Decorator.Effect>
                <DropShadowEffect BlurRadius="7" Color="White" ShadowDepth="0" />
            </Decorator.Effect>

            <ContentPresenter ContentTemplate="{TemplateBinding ContentTemplate}"
                    Content="{TemplateBinding Content}" ContentStringFormat="{TemplateBinding ContentStringFormat}" 
                    HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" RecognizesAccessKey="True" 
                    VerticalAlignment="{TemplateBinding VerticalContentAlignment}" />
        </Decorator>
    </Decorator>
</Decorator>

I created a ControlTemplate for a Label with the before-mentioned XAML, and used it everywhere I needed the text to glow.

How about something along these lines where you have a rectangle behind your text that blurs slightly, I have used this a few times. I find it makes it more readable because the blur covers a bigger area.

            <Grid>
                <Rectangle Fill="#8FFFFFFF"
                           Stroke="{x:Null}"
                           StrokeThickness="0"
                           VerticalAlignment="Center"
                           Width="{Binding ActualWidth, ElementName=PART_Title, Mode=Default}"
                           Height="{Binding ActualHeight, ElementName=PART_Title, Mode=Default}"
                           RadiusX="2"
                           RadiusY="2">
                    <Rectangle.Effect>
                        <BlurEffect Radius="10" />
                    </Rectangle.Effect>
                </Rectangle>

                <TextBlock x:Name="PART_Title"
                           Text="{Binding Title}"
                           Foreground="Black"
                           TextWrapping="NoWrap"
                           TextTrimming="CharacterEllipsis" />
            </Grid>