List of collective nouns
The phrase "An abomination of monks" is frequently cited as a legitimate collective noun for monks. It is actually a misinterpretation of the title of a protestant treatise written by Jan Hus around 1400.
An "anthology of prostitutes" is a pun on "anthology of prose", as "pro" is a common contraction for prostitute in Britain and elsewhere.
The phrase "A court of kangaroos" is frequently thought to be legitimate, given the (quite unrelated) expression "a kangaroo court". There is no known evidence of its legitimacy as a collective noun, however.