In my US History we're wrapping-up our unit on World War I and wrapping-up the grading period. At the end of each unit I like to post supplementary review materials on my classroom blog. I recently found two videos (actually it was one, but is in two parts) that provide a good overview of the causes of WWI. The videos are clearly older productions and are not something I would show during class time, but they have some value as a supplementary review materials for students to watch on their own time.
Part one is embedded below.
Here is a related item that may be of interest to you:
Three Good WWI Resources from the BBC