Internet Explorer 11 makes it very easy to add Windows Start Screen Live Tile support to a website via appropriately set META tags. An overview and links to more can be found at: http://www.buildmypinnedsite.com/en
I also made a Python+Django proxy site this year for National Novel Writing Month that demonstrates how simple this can be (http://github.com/WorldMaker/NaNoWriM…). I considered trying my hands at possibly offering a pull request for this, but there are a lot of aesthetic decisions to make and I mostly figured these decisions would be best in Newsblur’s own hands. Examples include the usage of high quality branding graphics, which tile templates to use and what to fill them with, how many different URLs to support (how deep the linking you want to have different Live Tiles for), etc.
Anyway, you may not have a lot of users like me using Windows 8.1 yet, but it is a simple and powerful way to make the website feel like “a real app” in Windows 8.1 and engage with users directly via the website without needing to implement a full application.