The naked mole rat is a fascinating creature, as introduced by Sir David Attenborough in Natural Curiosities. Not only are they mostly hairless, underground dwellers with a long lifespan for a rodent — 32 years! — but they organize their large groups based on a eusocial structure, like that of ants and bees. From wikipedia:
Only one female (the queen) and one to three males reproduce, while the rest of the members of the colony function as workers. The queen and breeding males are able to breed at one year of age. Workers are sterile, with the smaller focusing on gathering food and maintaining the nest, while larger workers are more reactive in case of attack.
Arguably, the Damaraland mole rat (Cryptomys damarensis) is the only other eusocial mammal currently known.
Dr Chris Faulkes explains more about the naked mole rat in this behind the scenes collection of clips: