Khan Academy
Khan Academy: Infographic: Chemical Abundances: The Sun
Did you know our sun in composed of mainly hydrogen and helium? This infograph reviews over all the chemicals that can be found in our sun.
US Department of Energy
Fus Ed Web: Physics of a Fundamental Energy Source
An excellent resource on nuclear fusion! Using incredible graphics and excellent discussion, this site (with its several pages) provides an exhaustive online course on the topic. Click on the link for "a Guided Tour" and begin.