Good free program to make YouTube photo montage?

I want to make a vid for YouTube, showing still photos at semi-regular intervals, with an mp3 of my own devising playing in the background.

Is there a free program that will make doing this relatively simple?

Thanks!

Picasa has a movie feature that you can add your own sound file to and a dedicated button to upload the finished clip to youtube.

Woo hoo! Thanks, blondebear!

As a second alternative, Windows Live Movie Maker (free download from Microsoft) can do that as well.

Openshot, too.