Thanks to Mike Potter, I found Comcast's "The Fan" application which is listed on their labs.comcast.com site and is serving up video clips and promotions for a lot of their cable content. The site was built using Adobe's Flex 2 technology, and is an excellent example of how big media companies are using Rich Internet Applications to enhance their properties and immerse users in rich media.
The portal itself is easy to use, you can build playlists of content by browsing through the genera of clips and then adding them. You can find items by content provider and also sort them by most played or most recently added. There isn't anything particularly groundbreaking about the application, but it's one of the few places I've seen where so much "big name" content is available in one place, and with so many genera. The video player also supports full screen, which is a nice touch.
Clicking on a video lists a series of related videos to the right of your playlist, so you can find content that's going to interest you. The social features are run of the mill, with a share button that allows you to email the video out and a link to a forum where you can discuss videos. There is no embed, no tagging, nothing that the other video sites have, but again, with the possible exception of Brightcove, no one comes close to having this much content in one place.
It looks like this will be for Comcast subscribers only when it launches, but it's good to see a major corporation experimenting with ways to give their customers more ways to access content. In a Rich Internet Application like this, it's about the content and the experience. This is just an alpha version, but I think the end result will be something that users will be very happy with.
If you're interested in why they chose Flex, code zen has a big write up on the project.