A gaggle of geese, an exaltation of larks! a herd of horses and a string of ponies, a colony of rabbits, a skulk of foxes, a leap of leapards, a cast of hawks, a knot of toads, a company of parrots, and a parliament of owls. A pod of seals, a mustering of storks, a labor of moles (are we getting closer?), a siege of herons, a crash of rhinoceroses, a trip of goats, a pack of dogs, a school of fish and a clutter of cats! Am I getting lost here?
It seems, thanks to Margaret, that a group of mice is commonly referred to as a family, and also as a horde, a mischief, or simply, and most frequently, a nest of mice.
Other collective nouns describing mice include a colony and a harvest. The former is self-explanatory; the latter from the fact mice and other rodents nest in the dry stubble of wheat and other cereal plants following the harvest.
A group of baby mice is called a litter.