For many years already, Java developers running Debian ignored the Tomcat bundled with Debian in favor of a manual installation. Nowadays, with the availability of Sun Java 1.5 in Etch, it is time to reconsider this.
Install Tomcat with aptitude install sun-java5-jdk tomcat5 tomcat5-admin tomcat5-webapps.
Edit /etc/default/tomcat5 to change the JAVA_HOME and TOMCAT5_SECURITY environment variables.
Note that you should consider reenabling the SecurityManager for production environments.
Now, you may install webapps into /var/lib/tomcat5/webapps and start tomcat with /etc/init.d/tomcat5 start