I'm wondering what is the multicolumn text control used in "News App", in Windows 8:
I have seen this microsoft example where they use fixed RichTextBlock and RichTextBlockOverflow inside a grid. There must be a better way to do this (I hope). Do you know how?
Unfortunately that's the best way to do it, if you are creating your app in XAML. However, if you are creating creating your app using HTML5/JavaScript you can achieve this using CSS Overflow Properties.
There is a video from the BUILD conference 2012, showing how this is done: Key technologies for building great reading experiences - the overflow part begins after around 20 minutes.
Note: The video talks about the possibilities and limitations of both HTML5 and XAML, and shows how it's done.