If you want to blaze some trails in Java EE, a great place to start is the Java EE examples gallery on the TomEE* website. What the examples lack in depth, they make up for in breadth. I'm sure you've all seen a basic CDI injection, but how often do you come across dyanamic datasource routing? Curious how it's implemented? Check it out!
* TomEE is an Apache Java EE 6 appserver assembled from various Apache projects (and I'm sure I lot of hard work)