Tomcat is a favorite of mine because I like writing Web applications in Java, and its so easy to quickly download and set up on both Windows and Unix-based servers.
Apache Tomcat 4.0, the Apache Software Foundations free Java application server (available at jakarta.apache.org/tomcat), was released last month. The Tomcat server supports the latest Java Web application programming standards, Java Servlets 2.3 and JSP 1.2.
Tomcat can run as a Web server (including SSL support for secure sites) on its own, or it can be used with all the main Web servers on the market.
Tomcat still has very few configuration or management tools— the Manager application that comes with Tomcat (which can deploy or list deployed Web applications) needs to have input typed into URLs submitted to the application.