Apache JServ Project
Java servlet module for Apache web servers compliant with the Sun Java Servlet APIs 2.0 specification. [Open Source, BSD-like]

The Jakarta Project
An Apache working group dedicated to providing a high quality, world class 100% Java Servlet and JavaServer Pages implementation. Involves ex-members of the old Apache Jserv Project and engineers from Sun, IBM, and other major corporations. Stable releases are now available. [Open Source, BSD-like]

Tomcat
The Apache developer community, Sun, IBM and others are working together to produce the official reference implementation for the Java Servlet 2.2 and JavaServer Pages 1.1 Technologies. [Open Source, BSD-like]

Just Go
Includes one-click launcher for Apache Tomcat on Win32 machines. Provides documentation. [Open Source, MPL]

Tomcat User Mailing List
Includes subscription information and searchable web archive of the Tomcat User mailing list.