This week's book giveaway is in the OCMJEA forum. We're giving away four copies of OCM Java EE 6 Enterprise Architect Exam Guide and have Paul Allen & Joseph Bambara on-line! See this thread for details.
Different servlet containers will name the jar file differently. Tomcat uses servlet.jar, but others may name it differently. Either read the documentation for your servlet container, or start poking around inside the jar files until you find the right one.