A parliament of owls (or baboons) and other collective nouns.

I recently acquired this Australian Geographic tee-shirt...

Haha... a eucalypt of koalas!
A dive of magpies (I can attest to that... I was attacked in this manner in Canberra, Australia)
A splash of crocodiles? More likely... A snapjaw of crocodiles!
A hang-up of fruit bats... I like this one best. Kim Ann added this alternative: A hangover of bats.

I then found this online:

A Pandemonium of Parrots: Collective Nouns for Animal Groups

http://blog.writeathome.com/index.php/2013/03/a-pandemonium-of-parrots-collective-nouns-for-animal-groups/

Li Peng, who freaks out at the sight of a single lizard... do note that when they gang up, you are up against "a lounge of lizards"! What about cockroaches? An intrusion of cockroaches! Methinks it should be "a creepy-crawly of cockroaches".

According to this list, it is a pace, herd, or drove of asses. I shall invent a new one: A butt of asses.
And, of course, a heehaw of donkeys. For horses... my choice is "A neighbourhood of horses".

Moving on to collective nouns for humans, I thought of:
A tissue pack of table chopers
A gossip of journalists (yes, that's true!)
A mindfield of psychologists
A couchful of psychiatrists
A conspiracy of theorists

Angie had this one:
A potful of gardeners
Me: A pot of snooker players

From Nick:
A boredom of civil servants
A SHIELD of Avengers
A train of ACS students (you have to be a local to get this joke).

From new mum Lynn:
A wail of babies

Lynn, how about this one too... A constipation of babies?
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For anyone with the patience, I found this very long list!...

http://www.ojohaven.com/collectives/

Actually, it is worth checking out... what is more apt than "an absence of waiters"!!
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Finally, I have been visiting too many people in the dental/medical line lately. I dedicate this short list to them:

A crowning of dentists
A knee-jerk of neuroscience specialists (sorry, this one is a private joke)
A lifeblood of haematologists
A cell check of oncologists
A heart throb of cardiologists
A pissful of urologists (they are always asking me to "double void, double void!")
An anal-ysis of gastroenterologists