Texas Education Agency
Texas Gateway: What Is the Universe?
The following tutorial is an explanation of what the universe is composed of.
University of Illinois
University of Illinois: Cosmic Mystery Tour
This multimedia tour is extremely dense with information about the origin of the universe. There are videos and simulations to assist with understanding, but it is definitely for advanced students.
Khan Academy
Khan Academy: Gallery: How Did Our Understanding of the Universe Change?
Understand how our view of cosmology has evolved by looking through different views of the Universe and zoom in on the light from distant stars on this site.