I had a Nikon D90 with and SB910 Speed light. To trigger my flash remotely, I had a Yongnuo remote trigger. I used to have a Ravelli tripod for my camera, but I recently upgraded it to a Vanguard tripod. As you know a remote trigger is really useful when the flash can be mounted on and easy to position anywhere. Now I am trying to recycle my old tripod to mount my flash and trigger it remotely. I am looking to find an adapter that would let mount my Yongnuo remote trigger on which I will mount my flash. Something like Ravelli Tripod head plate -> (an adatper) -> flash. Is there any such thing available?
You'll want a 1/4-20 thread if the tripod doesn't have one, then add a coldshoe, as Michael Clark wrote. For the coldshoe selection, I really like the enlight photo frio. It's not particularly cheap ($10-13) for a little piece of plastic, but it will positively lock the flash in place and since it's made of plastic I can toss it in the camera bag without worry about scratching other things.
While a cold shoe mount, like a Frio, is probably your best all-in-one solution, I'd actually recommend getting an umbrella swivel and stud. You can screw the stud onto the tripod (most of them will be 1/4-20 threaded on one side and 3/8-16 on the other), and then attach an umbrella swivel to the stud. This allows you to adjust the tilt of the light in a way that a cold shoe does not, as well as use an umbrella as a modifier. And, obviously, a lightstand would be a better tool than a tripod for mounting the light onto because most of us think of light as sunlight, and tend to place light sources overhead. Tripods, even with their columns fully raised, can rarely reach that high.
The main advantage of the stud and swivel is that that stud can screw onto anything with a 1/4"x20 or 3/8"x16 thread. So you could use a monopod as a light boom, or jerry-rig your own superclamps from Home Depot hardware.
If you've got another mounting plate for your tripod, you could use something like this:
I picked one up a while ago, and it works fine with ARCA-type plates.