A custom Javadoc Doclet which generates JSON of all the Javadoc info, so you can write your own documentation in any format and make use of existing Javadoc comments and project structure.

ant -p shows available ant tasks

Uses json-simple:
http://code.google.com/p/json-simple/

The goal is to implement all info available via the Java 1.6 API. If possible I will catch errors so that it can be used for Java 1.5.