Viddler is another good alternative to YouTube that provides better image quality and a unique commenting system.

The commenting system on Viddler is what makes it quite unique. Rather than posting comments in a list below a video, users can insert comments into the video itself as the video is playing. Let’s say you’re watching a video and have a reaction to a particular aspect of the video, you can insert your comment at the exact place in the video where the comment seems appropriate. (The video below demonstrates this better than I can describe it).
Viddler is also a recording service. With a web cam you can record video directly to Viddler. On most video websites you have to upload your video from a file created off line.

Here is a sample video from Viddler about the MacBook Air.