Put a Li'l Boom in Your Pocket: The Matthews Scissors-Clip
Hit the jump for more info and pics.
Here it is with nothing attached -- and upside down from its normal orientation. The grooved, "X-Wing" style base opens and closes to securely grab the panel-holding framework of a suspended ceiling, and drop down with a 5/8" male stud.
It'll hold any small light, obviously including an umbrella clamp and speedlight combo. Best yet, it wastes very little space beneath the ceiling before you get down to the strobe head. Which is usually a very good thing in a (low-ish) suspended ceiling environment.
An AlienBees light might be pushing it a little. (Please sound off in the comments either if you are doing that successfully, or had an AB drop and electrocute a subject.)
The little wire spring is a cable restraint. So if you stick a plug-in head up there, you can use a couple extra clamps to keep the cable out of the frame. Never had much use for that, as a few inches of gaff tape works just as well and takes up way less space in the bag.
But I will usually have two in the bag if I am headed to an office -- they are just too cheap and small not to. My Matthews brand clamp was less than $20, or you can get generic versions for under $10.
Here is a crop from the shoot which shows it all set up. It is serving as a mount for an umbrella swivel and an SB-800. The gaff tape on the flash head gobos it from flaring into my lens.
I can't remember what prompted this expression on John. I may be mistaken, but I think he was trying to remember the difference between "your" and "you're." Copy desk folks are picky about such things, you know.