If you're using Oracle 9i and JDK 1.4, you might be interested to know the recommended JDBC Driver is no longer classes12.jar (I just discovered it from the tomcat-user mailing list). The Readme.txt (at least on Win2K) in $ORACLE_HOME/ora92/jdbc states the following:
New classes file name for JDK 1.4 and beyond Beginning with this release the classes files for JDK 1.4 and beyond will be named ojdbc<jdk ver>.jar. So, the classes file for JDK 1.4 is named ojdbc14.jar. The names for the JDK 1.1 and 1.2 classes files will not be changed. We will not provide .zip versions of the classes files beyond JDK 1.2.