This site, developed by Kim Sosim of the University of Nebraska at Omaha, gives a common-sense treatment of demand and supply curves, as well as their determinants. (
http://ecedweb.unomaha.edu/Dem_Sup/demand.htm
)
If you'd like to practice your skills in various microeconomic topics (including demand and supply) using Excel spreadsheets, have a look at this site developed by Byron W. Brown (Excel required). For those students with a good mathematical background, these problems provide an interesting challenge. (
http://www.bus.msu.edu/econ/brown/pim/index.htm
)
The subject of "Spoilt for Choice" was a mathematician as well as an economist and is credited with developing a 'logical piano', which had many features later incorporated into 20th-century computers. His career is summarized at this site, which is part of the History of Mathematics Archive. (
http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/Jevons.html
)