For whatever reason, I could not get any of the above solutions to work. (Still can't.)
What I did instead was to include the jar in my project (blech) and then create a "system" dependency for it that indicates the path to the jar. It's probably not the RIGHT way to do it, but it does work. And it eliminates the need for the other developers on the team (or the guy setting up the build server) to put the jar in their local repositories.
UPDATE: This solution works for me when I run Hibernate Tools. It does NOT appear to work for building the WAR file, however. It doesn't include the ojdbc6.jar file in the target WAR file.
1) Create a directory called "lib" in the root of your project.
2) Copy the ojdbc6.jar file there (whatever the jar is called.)
3) Create a dependency that looks something like this:
com.oracleojdbc14system${basedir}/lib/ojdbc6.jar
Ugly, but works for me.
To include the files in the war file add the following to your pom