Depends on what you're running and what you want to do. If running Windows, you can try Windows Movie Maker. It's free and is about as easy to use as you can get. IIRC, XP has it built-in (may have to install it from the CD), but for Win7, you can download it free from
http://windows.microsoft.com/en-US/w...ssentials-home
Haven't done much video with Linux or Mac, so you'll have to wait for someone else to chime in, or Google for a popular one.