Sorry for the delay in answering (I've been slacking on the boards a bit lately).
The Ogre Kingdoms Army book allows for units of Ogre Bulls, Ironguts, Leadbelchers, and Maneaters to be fielded as Dogs of War units in other armies. Each one takes up a rare slot in an army allowed to field Dogs of War, with the exception of Maneaters who take up two rare slots.
You can download the current Dogs of War rules from GW here:Employing Mercenaries Download Page - GW (link, clicky, clicky)
This includes units of Dwarfs, Cannon, Heavy Calvary, Skirmishers, etc.
Hope that helps.