The recent upgrades to Google Earth beta 4 allows it to display time specific information and animation. A great example of this is the weather radar information available from the National Weather Service. The National Weather Service provides a number of dynamic data files that can be displayed in Google Earth. Their site provides an interactive web form that allows you to select a number of different types of files for various locations across the United States. These are dynamic data files, so once the file is saved to Google Earth, the information is updated over time. The FAQ page explains the various types of files and how to interpret them.
On Friday I was sharing this with a group of 4th and 5th grade students I was working with. Friday was a pretty rainy day in Portland and we speculated, based on the information we were getting from the Base Reflectivity file, if we would be able to go outside for lunch recess or if we would have to stay in. Just before lunch I pulled up the file again and based on the information we were seeing we decided that the rain would hold off until after lunch and we made the decision to go outside, and we predicted correctly.
While this type of data is available and displayed from within the NWS web site, the ability to pull it into Google Earth, combine it with other types of information and placemarks makes it a very interesting tool and resource for teaching.