Apogee Technical Publication #3 "Increasing the Descent Time of Rocket Parachutes." This easy-to-read report explains all the factors that determine how slow a parachute falls, and what you can be do to make them fall even slower.
Technical Publication #4 "The Science and Beauty of Streamer Recovery." This publication explains how streamers, made from readily available materials, can be constructed to make them fall slower. This provides a great starting point for many simple science fair topics.
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.sct.gu.edu.au/~anthony/kites/parafauna/chute_design/ Hemispherical Parachute design information
http://www.pcprg.com/rocketre.htm Parachute design for rocket recovery
http://www.angelfire.com/co/m2rules/paracalc.html Parachute descent rate calculator. Both Mac and Windows versions are available. (warning: lots of pop-ups)
http://www.pcprg.com/rounddes.htm Calculating descent for round parachutes. Something similar is also in the RockSim program.
Parachute Dethermalizers - These are devices that bring rockets down quicker so that they don't drift into the next country. Useful on smaller rockets (high school level)
http://www.sci.mus.mn.us/sln/tf/p/parachutingpinwheel/parachutingpinwheel.html Spinning parachute toy. May be a cool recovery technique if you can get it into a rocket and deployed properly.
Maple seed recovery technique. Plan for a simple rocket, similar to the Estes Tornado model. (middle school).
http://www.cs.indiana.edu/hyplan/jwmills/EDUCATION.NOTEBOOK/journal/journal.html Maple seed homepage. Can be used as a type of helicopeter recovery.
http://members.aol.com/ricnakk/paracon.html Parachute design and construction, particularly big fabric or cloth chutes.