Tomcat used to be under the Application Services, now it's hidden in Web > Enable Tomcat checkbox (talk about minimalist).
$CATALINA_HOME is in /Library/Tomcat The documentation (a whopping one page!) is wrong though, the port is not 9006, but 8080, since JBoss is no longer around, I guess. You also have to manually edit your tomcat-users.xml… grr…
There's also something missing from default Tomcat. For instance, an Apache FOP servlet would simply not work (it seems like there's some XML libs missing or something). Downloaded Tomcat 6.0.16, configured, everything works. Grr…
Also, don't use /Library/Tomcat/bin/shutdown.sh, launchd will come in and kick it back up (mega Grrr!). launchctl unload /System/Library/LaunchDaemons/org.apache.tomcat.plist is your friend.
Speaking of development platforms on Leopard, the PHP that's bundled, even though up to date, is useless for most corporate stuff since it's missing libgd so you can't do any graphics, including PDFs.