The Apache Jakarta Tomcat Server
Jakarta is a project of the Apache Software Foundation, and includes a number of subprojects, such as Tag{{`Libs, Hive}}`Mind, Slide, and JMeter, and previously included projects such as James, Struts, Ant, Lucene, and Avalon. Jakarta has its home page at http://jakarta.apache.org.
Tomcat was one of the Jakarta subprojects, is now a top-level project and and has its home page at http://tomcat.apache.org/.
FrontPage is a good starting point for reading more information about Tomcat, and is highly recommended.