Create a web application which connects to an ActiveMQ standalone server, package activemq-core.jar into WAR under WEB-INF/lib.
Deploy the WAR to a Tomcat 7. Then undeploy. In Tomcat manager press "Find leaks" button in "Diagnostics" section. Tomcat will complain that after undeployment some classes are still in memory.
Use profiler to locate WebAppClassLoader, see the screenshot.