A couple of weeks ago uvLayer (original writeup), one of my favorite AIR applications because of the visual effects and collaborative features, released an in-browser version that anyone can go and use. uvLayer is an interesting case because it started out as a desktop application and then they took that code and created the in-browser version of it to make it more accessible to a wider range of folks. You get most of the functionality from the AIR version but the AIR application incorporates native windows and allows you to "pop out" the video experience very easily.
In addition, uvLayer has been translated into 13 languages. When you log in, if you're not a fan of Flashy sites, you probably won't be too fond of uvLayer. It's a visual plethora of video and it can seem a bit overwhelming at first but they have a lot of features that I really like. It integrates instantly with Facebook so you can pull all of your Facebook friends using uvLayer and get an instant community. Once you've got the instant community set up uvLayer makes the entire video experience interactive and collaborative. You can create sets and then share them with friends. Then you can see what your friends are watching as it happens so you can quickly jump to videos. With a lot of friends you can be the first to get a sense of when a video is getting a lot of viral interest.
For media junkies, this is a great application and it's a fun way to watch video over the web. It definitely isn't for everyone but I think the YouTube crowd will appreciate the subtleties enough to give it some traction.