This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
They are tomcat/shared/lib and tomcat/shared/classes.
The hierarchy was simplified in version 6. I believe it's now just tomcat/lib
Be sure to read the release notes carefully. There is a section in there on JNI resources shared by multiple apps with some specific information on initializing them to insure that one app doesn't lock the others out.