Java SE (Java Platform, Standard Edition)

Hello all this is my first post here on the forums.

I'm trying to get some feedback on brainstorming a good applications to keep me focused in the world of Java.I just finished my spring semester of elementary data structures, and getting ready to take data structures in the fall. So im kinda looking for input on ideas for an application that could be a good learning experience. I am familiar with the use of netbeans, and have actually taken some minimal training on it(6.0.1), and I have also used Eclipse for most of the semester.

Been trying to think up some reasonably small applications that a 2nd year CS student may find useful, or could be a great learning experience.....Any Ideas?