Trebuchet.com  Great selection of resources including a Siege Machine video and catapult kits you can puchase. A discussion group too.

 The Algorithmic Beauty of the Trebuchet An amazing site put together by a true enthusiast.

 Anthony's Trebuchet page Another enthusiast with excellent information on construction etc

 The Grey Company Trebuchet page Incredible ampount of information on different typesd of Trébuchet as well as informtaion on how to construct one. There's even a black crow.

 NOVA On-line An incredible PBS site with video, animations and lots of information about the Trébuchet.

 The Realm of Taergerasmod An old site but check out the archived "plans" section; lots and lots of catapult plans from "easy" to "mayhem".

 Siege Engines  A great site that includes catapults and sundries such as armor etc. Also has a very active easily accessible discussion forum.

 Siege Engines of all types including Ballista, Mangonel, Perrier and Trebuchet; quite amazing. 

 The Trebuchet at N/F Observatory Interesting hisatorical piece about the Trébuchet being called the Ingenium in England (from which the word engineer came)

 Junk Yard Wars The Siege Machine was the very first episode in this very successful series. Alas, there appear to be no photos or more than the brief description  found here. 
 

Click on the Trébuchets below to see a slide show on the NOVA on-line PBS site

Click the medieval cartoon below to see the Grey Company's Trebuchet Links page.