Artilery through the ages - What are catapults? -
http://www.cr.nps.gov/history/online_books/source/is3/is3a.htm

How stuff works - How do catapults work? -
http://science.howstuffworks.com/question127.htm

Marshmallow catapults - Made from milk carton -
http://www.usoe.k12.ut.us/curr/science/core/plans/int/grape.html

Build a catapult - Family fun - http://familyfun.go.com/parenting/learn/activities/feature/famf199611_learnproj1/famf199611_attendants.html

Build a marshmallow catapult - Math Central -
http://mathcentral.uregina.ca/RR/database/RR.09.96/gareau1.html

Catapult Gallery 2003 - http://www.patriotpv.com/Simple_Machine_Webquest/Simple%20Machine%20Webquest/Catapult%20Competition.htm

Motion, Forces, Energy and Electricity -
http://school.discovery.com/lessonplans/programs/motionforces/

Catapult Project - Applied Technology -
http://www.members.shaw.ca/applytech/at/catapult.htm

Catapult Experiment -
http://www.cosi.org/ossw/2001/experiments/catapult.htm

Rubber band catapult-
http://www.newton.mec.edu/Brown/TE/CATAPULTS/Catapult_unit.html

Another Marshmallow catapult -
http://ms.kmsd.edu/~science6/projcata.htm

The physics of catapults - middle school project -
http://hale.nrsd.net/Catapult_Project_Kelly.htm

High school made catapults -
http://www.wsd1.org/DMCI/other/catapult/catapult.html

Sixth grade catapults -
http://reading.hccanet.org/hilltop/photoalbum.html#catapult

Lots of various catapults to build -
http://www.knightforhire.com/catapult.htm