This week's giveaway is in the EJB and other Java EE Technologies forum. We're giving away four copies of EJB 3 in Action and have Debu Panda, Reza Rahman, Ryan Cuprak, and Michael Remijan on-line! See this thread for details.
CATALINA_HOME is an environment variable that Tomcat uses. If you're using Java 5.0 or newer, you can get the value by using the method java.lang.System.getenv(...). Look it up in the API documentation.