RAM, Garmin(on RAM mount), and Touratech all from what I've read. I have the RAM and like it. Never heard a complaint from it. I've seen one broken Garmin and read of another. Its attaching mechanism is not well designed.
I don't like the Garmin much, because it "secures" the unit by a tiny piece of spring steel that grabs a flimsy piece of plastic on the back of the unit.
The RAM bracket is a bit more bulky, but still very light and feels much more secure.