Overstream is a wonderful site for adding subtitles/comments to a video. This is done w/ a very innovative user interface that looks a bit like iMovie HD. For example, a user can upload a web video via URL, and then select the start/stop time of adding text (similar to splitting a video clip). Once a video is done it can then be shared online in Overstream or embedded into a site/blog.
I highly recommend checking out Overstream by clicking here!!!