Collective Nouns

It is amazing just how many collective nouns there are in the English language. We have a murder of crows, a belt of asteroids, a flight of stairs and a den of thieves. However, there are a lot that we don't have... officially.

Here are a few suggestions to fill the some of the gaps:

• A blaze of firemen
• A smothering of Social Workers
• A gathering of combine harvesters
• A shoal of nudists
• A collection of philatelists
• A camp of bell-ringers
• A herd of listeners
• A number of mathematicians
• A drift of castaways

Any more for any more? For example, what is the above group of collective nouns called?