A neat tool to use in collaboration with Flickr is Time-lapse Creator. The idea is rather simple. Take your pictures, upload them to Flickr, then use the Time-lapse Creator to put together a time-lapse of your photos. I know that there are several districts who block access to Flickr, so teachers and students might have to work on it at home to put the time-lapse together.
I could see this being used in science classrooms taking time-lapse photos of experiments catching reactions or in Earth-Space Science classes showing the hydrologic cycle process. I could also see it used in geography classes to show change over time as it relates to climate. It would be neat to setup a camera and do a similar time-lapse of weather patterns outside your school. If you teach Art, it might be worth while to have students take pictures of a project as they work on it.
You will have to sign in to Yahoo to use this service.