I was able to bake bread with my son for the first time in about 6 years (I'll post about this separately), and while doing so I did a simple yeast experiment.  I placed some yeast in plain warm water and some in warm water with sugar and asked him to observe what happened.  Well, of course, then I had to go online so I could explain what happened since I just know that it works. LOL!  Here are the results of my research thus far:

Science Study Resources- Yeast

Exploratorium- Bread Science

http://www.exploratorium.edu/cooking/bread/bread_science.html

See images of microscopic yeast cells, learn about it’s leavening action and view experiments using both yeast and gluten at this website. 

The Science of Yeast

 http://www.lesaffreyeastcorp.com/SoY/

Sponsored by Red Start, this website offers resources for educators and students, an image library, suggested experiments, and a description of the manufacturing process.  The site provides a printable 7-page summary titled “The Story of Yeast” with a diagram detailing the process for making nutritional yeast. 

Yeast Genome

http://www.yeastgenome.org/VL-yeast.html#non-specialist

This website offers an extensive collection of links to various resources to assist you in learning more about yeast.  Caution: The site offers links and information on several forms of yeast, not just those used for baking. 

Bread World

http://www.breadworld.com/Science.aspx 

This site provides a summary of the history of yeast and how it is manufactured today, sponsored by Fleishman’s. 

Understanding Biology

http://www.york.ac.uk/org/cnap/ubiology/proj7_bugbox.htm

These instructions for using the “Bug Box” found at this website can be followed using materials you collect yourself and the printable worksheets provided by this UK website, Understanding Biology.  The program is designed to teach elementary grade students about life processes and living things.  Additional links are provided (at the website and copied below) to assist the instructor in demonstrating the activities of various microorganisms:. 

http://www.cellsalive.com/howbig.htm - animation that zooms in from a pinhead to a virus
http://www.bbc.co.uk/history/historic_figures/pasteur_louis.shtml
http://www.historylearningsite.co.uk/joseph_lister.htm
http://www.bbc.co.uk/history/historic_figures/snow_john.shtml

http://www.microbiologyonline.org.uk/faq.html
http://www.schoolscience.co.uk/content/4/biology/sgm/sgmmicrobes2.html - web page showing pictures of different shapes of bacteria
www.denniskunkel.com – excellent electron microscope images of bacteria, viruses and fungi

http://www.science-projects.com/dairybacteria.htm - lists bacteria used in dairy products
http://www.schoolscience.co.uk/content/4/biology/sgm/sgmfoods0.html - this webpage shows a café scene giving information about microbes in food

http://archive.food.gov.uk/hea/index2.html - excellent resource with quizzes and activities covering the basics of food hygiene

Close up image of commercially prepared yeast

http://www.all-creatures.org/works/yeast.html

Yeast as a biocatalyst

http://www.irishscientist.ie/2000/contents.asp?contentxml=187s.xml&contentxsl=insight3.xsl

Making your Own Yeast

http://www.appropedia.org/Yeasts_for_Baking