Well, YUM stands for Yellow Dog Updater, Modified, so obviously, Yellow Dog uses it. Other than that, I don't know of any distros that use it off the top of my head (although some of the popular RH based distros may...)
As for RPMs, just about all of the RH based distros can use them in one form or another. This includes and is not limited to Fedora, SuSE, Yellow Dog, and Mandriva.