There are many lists of collective nouns for animals, but these rarely distinguish between those in genuine current or historical use and those merely mentioned in older lists (often fanciful, sometimes just jokes, and sometimes spurious or resulting from misunderstanding).
Since there is a certain amount of popular interest in this arcane topic, the OWLS has compiled a list of a large number of collective nouns for animals listed in various sources.
The most commonly cited collective term for cats is clowder.