JayCut a try. It's a full-featured video editor on the Web.
JayCut's features are surprisingly sophisticated for a free, Web-based application. While it doesn't replace expensive software like Apple Final Cut or Adobe Premiere, it does offer two tracks, to which you can add video clips, audio, text, and transitions. You can also record audio and video directly from your computer's microphone and Webcam. When you have finished editing you have the option to export your video directly to YouTube, or to your computer in the form of an H.264 MPEG-4, H.264 Flash video, or an Xvid AVI file.
If you need to save a project to revisit later, simply create a free account.