Here is a list of known useful third-party tools and add-ons.
UrlRewriteFilter by Paul Tuckey (also hosted on googlecode) is a Filter that performs URL rewriting and redirections, and other typical tasks, like setting request attributes, headers or cookies.
It is similar to mod_rewrite module of Apache HTTPD server.
SecurityFilter is a Filter that mimics container managed security.
Spring Security is a powerful and highly customizable authentication and access-control framework. It is usually used with Spring Framework. In simple configuration it may be used as a filter to perform both authentication and authorization. It also can be used to perform authorization control at business methods of an application, and to implement domain object security.
psi-probe is advanced manager and monitor web application for Apache Tomcat.
(It is a fork that continues development of the Lambda Probe application. The original Lambda Probe project is no more active since year 2006).