Bernouilli's Principle,
control surfaces and paper airplanes, navigation, meteorology,
propulsion, Charles' and Boyles' Laws, and more.
The Java Virtual Wind Tunnel which uses computational fluid dynamics (CFD) methods
to simulate the flow of air over a two dimensional object.
Written by Craig Hunter, Aero- and Gas Dynamics Division, NASA
Langley Research Center.
The heart -
http://www.fi.edu/biosci/heart.html. A
site devoted to the most important pump and fluid in your life.
The structure and development of the heart as well as cardiac
health are presented at length. A killer reference site, the
medweb cardiology site
is referenced here