Non-Gunpowder Artillery http://xenophongroup.com/montjoie/ngp_arty.htm
The history of medieval mechanical artillery and war machines with comment on historical accuracy, plus diagrams and information on the specific uses of each type of machine.
Ron Tom's Trebuchet Page http://trebuchet.com
Lots of information about trebuchets and other leverage artillery.
Siege Artillery http://198.144.2.125/Siege/siege.htm
Ancient siege artillery engines, with pictures of replicas, instructions for building them and historical information.
