BestPig released a new version of freeBOOT ToolBox - a tool that allows to create and customize a freeBOOT image based on an original or XBR/freeBOOT dump:

A small update that will just add support for the 12625 kernel thanks to fbuild 0.20.
Official Site: http://www.bestpig.fr (the interface is also available in English)
Download: n/a (might be illegal under DMCA/EUCD)