Animoto is one of those sites that I have heard about and used for a while, but never wrote about. So here goes.
Animoto is a very cool site that allows you to create video slideshows. The free version does have a limit of 30 second videos but the Plus plan is only $5 per month and has full length videos. There are more expensive plans that include more functionality also.
You select images and musics and video clips and then Animoto organizes them into a video slideshow. You can also share your slideshows through a variety of social media sites and there are some nice design backgrounds to choose from.
UPDATE: there is a free Animoto Plus account for educators. It removes the 30 second limit you get on a normal free account and allows you to create student accounts. See it at http://animoto.com/education