The Russians have a few models, but all are considered "Experimental" and were never put into production.
The best-looking one was listed on tihs thread but I can no longer find the pics:
RPK-74 plastic drum mag *PIC*
DOES ANYONE HAVE A COPY OF THE PICS?
This is the featured 5.45 drum - not only is it an interesting design, it also demonstrates the belt-fed unit's ability to take standard magazines as a backup:
Also found this one: