Seems like Maven is gathering some ground as a build tool. One clear indication of this has been the increasing flow of questions on the OTN forum about how to work with JDeveloper and Maven based projects.
The basic scenario is that a company decides to use Maven as their build tool, and developers who are using JDeveloper are usually wondering how to map the Maven directory structure to a JDeveloper project.
Luckily for them the guys who are working on Trinidad faced a similar problem and created a Maven plug-in that creates a JDeveloper project file (jpr) based on the Maven project.
Using the plug-in is quite trivial, but when people are googling for information about "JDeveloper and Maven" they get pointers to old docs that talk about the old Maven1 JDeveloper plugin.
To fix this situation, we now have a new Maven and JDeveloper how-to that will show you how to get the plug-in and how to use it, as well as how to run maven builds from inside JDeveloper and how to get code insight when working with the pom.xml files. I hope this will help.
update Jan 2011 - note that there is now a Maven extension to JDeveloper that you can get through the help->check for update.
I updated the link above to point to a new tutorial that covers the basics of working with this extension.