I was playing around with the Windows Phone 7 tools and noticed that there are some system styles available for text.  For example, I noticed the following XAML that referenced PhoneTextTitle1Style in one of the Visual Studio project templates:

            <TextBlock x:Name="ListTitle" Text="{Binding LineOne}" Margin="-3,-8,0,0" Style="{StaticResource PhoneTextTitle1Style}"/>

I then wanted to figure out what all the system styles were.  How to do it? Expression Blend!  By going to the Assets tab and then clicking Styles --> System Styles, I was able to see all the styles:

 

I then wanted to see what they looked like, so I double clicked each one, which created a textbox. To correlate the look with the name, I replaced the default text with the name of the style, producing this:

 

Perhaps this graphic/tip will help someone out there!