Well, this is a new one on me -- a so-called world passport issued by a DC nonprofit, not by any country authority. They claim it's legal and has been accepted by many countries, both officially and on case-by-case bases. A short excerpt from the description:

The World Passport is...a meaningful symbol and sometimes powerful tool for the implementation of the fundamental human right of freedom of travel. By its very existence it challenges the exclusive assumption of sovereignty of the nation-state system. It is designed however to conform to nation-state requirements for travel documents.

If you look around the site you'll see they have lots of other documents, such as a birth certificate, ID card, marriage certificate, and even a political asylum card.

Personally, I think it's a great idea and really does embody the idea of being a true world citizen. It even uses Esperanto as one of the languages! It contains the country of birth, but not the country of residence.

That said, I'd never actually try to use it as a travel document. Any FTers out there have one? Anyone try to use it?