JayCut is a remarkably full-featured video editor for the web, comparable to something like iMovie or Windows Movie Maker. You have two tracks, to which you can upload and add video clips, audio, and add text and transitions. You can also record audio straight from the webapp with your microphone, as well as video from a webcam. After you're done, you can publish your video to YouTube or export it to your computer as H.264 Flash video, H.264 MPEG-4, or an Xvid AVI.
…, transitions need to be placed between videos on separate tracks overlapping one another, and you can only preview your movie from the beginning instead of placing the playhead somewhere. If you want to save projects and come back to them later, you need to create a free account. Also note that I had some weird issues in Firefox trying to export my video—it wouldn't let me input my information—so you might want to run a quick test in your browser of choice before editing a 3-hour masterpiece. -Lifehacker