Is there any tutorial/documentation on building a ground up application
using Oracle (10g) back end, where PL/SQL procedure are exposed as Web
Services via Tomcat which are then called by a Java application/front end.

I know this can be done (fairly easily) with JDeveloper and OC4J, but I
want to try Tomcat.

Alternatively, it is true that Web Services can be implemented/exposed
directly inside the database with 11g, in a similar way as APEX on 11g
doesn't require OHS?