Hello,
Tired of C programming ? Want a more beautiful language ?
Xavier Grave has converted the simplest version of SOS (http://sos.enix.org) in Ada !
You can compile it using gnats, it is using Grub as bootloader, and it prints a message to the screen. For the moment, it is not possible to use the Object Oriented possibilities of Ada.
URL : http://ipnnarval.in2p3.fr/~xavier/
By the way, if you are aware of OS programmed entirely in Java (using gcj), I would be particularly interested.