video://www.youtube.com/watch?v=4YsQ6f125GY&feature=player_embedded
YouTube, my favorite online video site, is now allowing you to edit your videos online using their new beta tool. Right now you can edit videos (that you have uploaded) to make a new video with audio of your choice. Now if they can add more features like adding custom logos, I would start using it all the time.
If you want to try it, go here.