I used hack on the Jewel window manager, and started working on porting the C++ code to ObjC and tidying how it works, unfortunately I've not had enough time recently to get anything usable (or even ready for public viewing) out yet. At the moment this project is somewhere near the bottom of my list of projects.
For the current status on the jewel project visit: http://mjr.towers.org.uk/xwinman.html