Apple has begun rolling out iTunes web previews for fourth generation Apple TV apps. The move, which was first spotted by Jeff Scott (via MacStories), will allow both users and developers to easily share links to Apple TV apps on the web.
It doesn't appear that web previews are available for all apps yet, and it's unclear which apps it's working for—Apple isn't advertising them anywhere. If you want to see what they look like, here's a link to Scott's app for Beergeek.com TV.