For articles on this subject check out the Peak of Flight index. This is a list, by topic, of all of the great articles the Peak of Flight put out over the years.

http://www.geocities.com/nzrocketman/rocketscience.htm - Explanation of the forces that act on a rocket during flight. Lift, Drag, Gravity, and Thrust. Also discusses stability, and what it means to be: stable, unstable, neutrally stable, and dynamically stable.

http://web.syr.edu/~smdemar/rocketdrag.html Model rocket drag analysis using a wind tunnel to make measurements(high school level).

http://www.lerc.nasa.gov/Other_Groups/K-12/windtunnel.html Explore how to measure drag with this NASA wind tunnel web page. There is also a link to NASA's FoilSim software, which can be used to simulate an airfoil in flight.

http://members.aol.com/hfdy/home.htm This is where you can purchase the classic book: "Fluid Dynamic Drag" by HOERNER.

http://www.desktopaero.com/appliedaero/preface/welcome.html "Applied Aerodynamics: A Digital Textbook" (college level)

http://aero.stanford.edu/WingCalc.html This Java application computes the lift and C_l distribution over a wing with sweep and twist.