My main focus for a while has been working on a Java port of the popular PROJ.4 projection library. This was motivated by finding the great work that JHLabs started with his JavaProj port. That seemed too good to be left to languish, so I dusted it off and started to clean it up. The library is now known as Proj4J. It has been substantially reworked to provide a more functional API and a cleaner codebase. Various bug fixes have been made to the core projections (although more remains to do!), and a formal test suite has been added.
To answer the question of "Why another Java projection library?", the main reason is that PROJ.4 is popular, well-tested and well-documented, so it seems like a good idea to make it available in the Java world. Other goals include creating a small, easy-to-understand, easy-to-use library, which can be embedded and/or extended as desired by small projects. A personal goal is to provide coordinate system transformation services in JEQL (which is now realized by exposing Proj4J via JEQL functions).
OSGeo is hosting the codebase as part of the MetaCRS umbrella project. There it lives in the good company of Proj4JS, CS-MAP, spatialreference.org and of course PROJ.4.
The code is shaping up nicely for a 1.0 release. It can also be downloaded and used as it stands. Check it out! Even better, contribute some tests and bug fixes!
Wagner VII Projection