<p>I need to scale calls into Tomcat and it's been suggested to launch threads internally.  Has anyone needed to do this and, if so, what solutions did they come up with?</p>

Your question is a bit vague. Tomcat itself already uses a thread pool to service HTTP requests. You can increase the number of threads through Tomcat configuration - look to the Tomcat wiki for info on this.
If you mean that in your code you want to launch threads, then I advise perusing the java.util.concurrent API introduced in Java 5. Also read "Java Concurrency in Practice", which is
the
text on this subject.