YouTube has introduced Online Video Editor. Google announced this today. Though already a few video editors I have seen online, this one is damn simple to use and integrated with YouTube. But downside is, it is not just a standalone application, it is a feature of YouTube, so that we can edit our video in YouTube with a huge collection of Audio libraries also. It supports some very basic features only like Combining multiple videos in YouTube, cutting scenes in a video and Adding an audio track.
Hope the future version will bring more features and also function as a standalone Video editor.
Here are some screenshots (click the image to enlarge).