Is there such thing as a freewheel that doesn't click? The clicking sound of the freewheel on my singlespeed when it's coasting is annoying for me, so I flipped over my back wheel and rode fixed for a few months in blissful silence.  But having to pedal all the time even when going downhill, over bumps and around corners, was probably even more annoying - so today I am flipping it back again to the freewheel.  Then I wondered, is there any such thing as a silent freewheel hub that I can buy?  If so, what's the search term I'm looking for?
As already said, Shimano used to manufacture Silient Clutch rear hub. But that has been stopped a few years ago, so if you manage to source one - you are lucky man. 



I used to have one of them and it was truly silent. It was heavier than standard shimano LX hub, but it was silent and with instant engagement.

Also I used Chris King hubs. If you put a lot of grease in their mechanism - they also become silent. 
Pretty much with most of the freewheels, if you put a lot of thick grease in them, you'll silent them for some time. Unless you ride Hope hubs -)

I've heard about Stealth hubs - they are claimed to be silent, but I never had a chance to try them out. 

You might as well read this thread about silent hubs for further information.