A Brief History of the Timpani
This informative article traces the timpani from the kettledrums used during the time of the crusades. It discusses both the mechanical development of the timpani as well as the various uses composers made of it. There is a wonderful timpani FAQ here, classified into answers for professionals, students, and laymen, and links to related sites that list timpani literature.
World Carillon Web Site Index 2000
Here's an extensive list of the carillon bell locations all over the world, together with links to the Web sites whenever possible. There are links to international carillon societies, the Netherlands Carillon School, and also to various bell foundries.
This page consists of an illustrated history of the castanet, from Paleolithic ivory castanets to modern manufactured models. It also explains the parts of the castanets and gives some tips on maintenance. Note that a non-native English speaker wrote this page.
This Encyclop‘dia Britannica article explains the history and development of the cymbals through text, charts, and sound clips. There are also plenty of links to related articles on military bands and musical compositions in which the cymbals play an important part.