What is JavaBlackBelt:

JavaBlackBelt is a community for Java & open source skills assessment. This is the place where Java developers have their technology knowledge and development abilities recognized. It is dedicated to technical quizzes about Java related technologies.
The folks over at JavaBlackBelt are doing a lot of good work. As of right now they have nine tests ready to be taken and seven more in beta or otherwise under development. Today I decided to take some time out of my day and take my first test for a yellow belt. It thought all the questions were well thought out and the framework in which the Exam was presented in was very straightforward.

These folks are serious about this so I encourage people who may be interested to get involved. One aspect of the higher level tests I found especially interesting was the need to contribute. Each time a user submits a question that is reviewed and accepted by a moderator or for each question reviewed by a user a certain amount of points is credited to your profile. These points can then be used to take certain higher-level tests.

I've talked about this site before so check it out.

Reference: JavaBlackBelt.com: Martial Arts Meets Hardcore Code