Without the Sun there would be no photosynthesis, no green plants no oxygen and no humans...
http://photoscience.la.asu.edu/photosyn/Default.html
Arizona State University Photosynthesis Center: information on various
research projects and virtual experiments.
http://www.pbs.org/ktca/newtons/9/phytosy.html
From PBS's "Newton's Apple": easy to understand explanation of
photosynthesis and activities for elementary or middle school.
http://www.waterw.com/~science/october.html
Clear description of photosynthesis, why leaves change color in fall, and
activities.