I have been trying to find documentation to give to our developers that outlines things that would be of interest to developers moving from Oracle 90i to 10g. I have found several vendors including Oracle that offer classes on the lines of "Oracle 10g New Features for Administrators" but can not find anything aimed at developers.
Each book in the documentation set generally contains a section at the beginning called What's New in <Topic> that details the new feautres for that topic.