I've been a user of iMovie for years but now my kids are cranking things out too.
http://www.youtube.com/watch?v=jx_8zZY41o0The fact my kids can record video (via the iMac's built-in camera), add audio clips, make transitions, crop, edit and build a full video story shows the easy-access and power of this brilliant software. There are many neat PC apps out there... but Apple seems to consistently and creatively lead the way.... and with FREE software (when you buy an Apple).
One word of caution, use the old iMovie HD version (you can still download it from Apple), the 08 version that shipped this last year with the Apple OS has less features and is geared towards quick and less sophisticated productions (Google this topic for the details). iMovie 09's reviews are more promising. Interesting, the
NY Time's Tech personal tech writer, David Pogue uses iMovie and produces his own video segments.