For sensored motors, there seems to be three major companies making motors. Novak, LRP and Feiago. So far as we all know, Novak and LRP do NOT OEM their motors to other companies, and only sell them under their own brands, with LRP also marketing under the Nosram label.
Feiago seems to be where everybody else is going to get their motors right now. This includes: Orion, GM, SpeedPassion, and possibly others. The Feiago motors are generally easy to spot, as they have oval vents cut into the can, and have a rotor with an internal fan attached to it. Supposedly each company that OEM's these motors can put their own tweaks on things, however the only one that seems to be readily available at the moment is Orion's flavor, so there hasn't been much comparison between them.
We've seen pictures of a sensored motor with a Checkpoint sticker on it in use by Marc Rheinhard, with rectangular vent holes cut in the can. It's not apparent where this motor is sourced, but I suspect it may be Sagami (of Japan) as that seems to be the source of the sensorless Checkpoint motor we saw Hara using recently. That's just a guess, though.
I believe we also saw a sensored setup on a Losi car that looked unique as well. I wouldn't be surprised if Spektrum releases their own sensored brushless system at some point in the future, possibly with their own motors.
I also heard that Hacker is working on their own sensored motor, and saw a few early pictures, but nothing since then.
If you start talking sensorless, things get a lot more complicated with a lot of other companies in the mix, and some uncertainty about who's making what.
When it comes right down to it, all the motors seem pretty similar in performance. The tweaking appears to be minimal, mostly with air gap and default timing. I imagine we'll see more tweaks in the future, but we've been at this brushless thing for a while now, and very little has changed so far.