Capture Online Videos

I need to capture videostreams from sites youtube, myspace, vimeo, dailymotion, [login to view URL] as a flv or mp4 file using a save file dialog. I want the video saved much like real player saves any video from various sites. Since some sites downloads videos in chunks the video stream needs to be saved continuously until the video finishes playing. The video can be saved by downloading each file part and dynamically joining the parts until the video is complete or by capturing the video from a hidden browser or player in a continuous stream to create the new flash video or mp4 file or by creating a custom web browser with it's it's own cache folder and saving the flv file to it's own cache location. Whatever works. Just looking for the end result of having a video download program. Code needs to be delivered in Vb.Net 2008.