I know this is an old post, but I wanted to post a recent experience (2011) since it's still a tool SLMS's may want to use. This is just an FYI.
Animoto is super easy. The good things are you pick your music and load your images and it puts it together for you. You can pick the speed and the resolution. And it's easy enough for me to teach my 3rd grader how to make one no problem. You can drag pictures around in the order you want them.
The bad things are 1. You can't control the timings like you can in Movie Maker, so my 3rd grader's podcast audio of Mississippi set to pictures didn't always line up with what he was saying. But it's fine if you use just music, just not words or discussions. 2. You get 240 res but to get 480 you have to pay $3. 3. It takes forever to process.
There are a limited amount of themes you can pick and I think they have educator accounts like with wikispaces, glogster and edublogs. It's suppose to be an upgrade to a regular free account. I like it for quick and easy projects. If you use it for a whole class though, you may not want to pay the $3 to make the video bigger.