Windows Phone 7 was a pretty capable platform that never really took off, especially when it came to game support. Of course, market share is a big part of the reason was the lack of applications ( although it is easy to get in a chicken and egg argument, whether market share suffered because of the lack of app support, which suffered because of the lack of market share… ).
With Windows Phone 8 however, Microsoft have rectified at least one of these problems. You can now compile native C++ code. This means a gigantic collection of existing libraries can be ported to or now target the platform.
And ported they have been, here is the list to date. Keep in mind, pretty much every single project that runs on Windows 7 will run on Windows 8 Desktop, so “Windows 8 support” is a pretty meaningless statement. The following are all products that will support Windows RT, the artist previously known as Metro. Or in more simple terms, you can use the following to make games for ARM powered Windows 8 devices.
If I have missed any, please let me know!
(All products) http://www.havok.com/news-and-press/releases/havok-showcase-full-technology-suite-windows-8-windows-rt-and-windows-phone
(road map only at this point)
Somewhat related or slightly less game oriented products that added Windows 8 support