I dislike certifications. They usually have a nuisance value more than anything else. But I was pleasantly surprised when I chanced upon Java Black Belt, a developer community based site that offers certification.
Their focus unlike most other approaches is not theoretical, but geared towards the practice of programming. The questions are created by the community following a moderation and rating process. They do not charge money for the tests, but require volunteer points. Volunteer points can be earned by helping them refine questions, proposing new questions, and even by contributing to open source projects. This goes very well with the philosophy of participation. Volunteers help develop the site, learn in the process, and also get certified. As participants pass tests, they gather knowledge points, and as they gather knowledge points and pass tests, they attain advanced belts, corresponding to their levels of mastery.
If this seems interesting, and you are already getting curious, then do not waste any more time, go straight to their website.