Animals:
* Clowder of cats
* Covey of quail
* Creep of insects (specifically caterpillars)
* Clutch of eggs
People:
* Chorus of singers
* Congregation of worshippers
* Company of actors/performers
* Crew of sailors/workers
* Clique of friends
Things:
* Cluster of grapes/stars
* Cloud of smoke/dust
* Collection of stamps/coins
* Coterie of artists/writers
Other:
* Cast of characters in a play
* Colony of ants/bees
* Congress of nations
* Constellation of stars
Let me know if you'd like to see more examples!